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THE subject with which this book is concerned is one 
of vast extent and enormous importance. It covers 
wide tracts of territory in physiology and medicine. 
" All life processes," as Prof. Wolfgang Ostwald has 
summarily said, " take place in a colloidal system," 
and that is true both of the normal fluids and secretions 
of the organism and of the bacterial toxins, as well as, 
in large measure, of the reactions which confer im- 
munity. If this is so, it would seem to be an obvious 
desideratum that the drugs employed to combat disease 
should be in the colloidal state, i.e. in a form in which 
they may be isomorphic and isotonic with the elements 
of the body. Only so can they be expected to exert 
their full potency. The task of thus bringing their 
remedial virtue to its highest point is not an easy 
one, for colloidal substances, unless prepared with 
consummate skill and meticulous care, lack stability, 
and are prone to precipitation when brought into 
contact with the electrolytes normally present in the 
body tissues and fluids. That it is not beyond the 
resources of scientific chemistry is clearly shown in 
this book. A measure of success has, in fact, been 
achieved which leaves no doubt of the brilliant future 
which lies before drugs in the colloidal form. 
To the study of colloids, both in health and disease, 


some of the world's greatest investigators have devoted 
and are devoting their genius for research. Much that 
was mystery has already been elucidated. A very 
considerable body of literature has accumulated, and 
the time is ripe for such lucid expositions of ascer- 
tained results as will be found in these pages, written 
by an acknowledged master of the subject. 


THE present volume is based on a lecture delivered at 
the request of the Chadwick Trustees, under the chair- 
manship of Sir William Collins, K.C.V.O., and forms one 
of a series of works published under their auspices. 
Some of the information also appears in the author's 
contribution to the British Association Report on 
Colloids, viz. The Administration of Colloids in Disease, 
published by the Department of Scientific and Indus- 
trial Research, and obtainable from H.M. Stationery 




November, 1919. 


FOREWORD ......... 

AUTHOR'S NOTE ........ 

OF COLLOIDS ....... 










X. CONCLUSION ....... 













THE difference between a healthy and a diseased 
organism is so important, and the necessity for im- 
proving the health of the nation is so urgent, that any 
application of knowledge to this end is worth very serious 
consideration. Consequently it is necessary that any 
possible use of discoveries in branches of science, 
other than medicine, should be brought to the atten- 
tion of all concerned with the least possible delay. 
This application of knowledge gained in various fields 
of investigation to the improvement of health and the 
reduction of disease was one of the foundation prin- 
ciples of Sir Edwin Chadwick, whose generosity made 
the present publication possible. 

The study of hygiene and of many diseases has been 
enormously facilitated by the discovery that many of 
the ills that flesh is heir to, and many others which it 
is unnecessary to suffer, are due to the influence of 
bacteria and their products. There is, however, a 
still wider cause of disease, of which bacteria form 
only a part, which is due to the peculiar structure of 
the essential organs of all animals and vegetables a. 


structure which has long been recognised in certain 
ways, though some of its properties have only been 
realised within the last decade or two. 

We are all aware that living organisms are com- 
posed of a number of cells consisting of an external 
envelope, or membrane, and an enclosed fluid. Even 
the most complex animal structure can be shown to 
consist of a vast number of such cells, differing enor- 
mously in their shape and functions, but all possessing 
certain well-defined characteristics. The membranes 
or envelopes of these cells possess the peculiar property 
of allowing certain substances to pass through them 
quite readily whilst others cannot do so, and on this 
property depend many of the most complex functions 
of the whole organism. The processes of digestion and 
assimilation and the oxygenation of the blood are 
well-known examples of the selective passage of certain 
substances through the membranes concerned. Some 
investigators, including Moore and Roaf, 1 do not 
accept the idea of membranes of selective permeability, 
but consider the phenomena usually attributed to 
them as being due to selective absorption. This 
appears to be specially applicable to living cells, as 
several colloids behave differently in these from what 
they do in synthetic, or " dead," membranes. 

It is well known that if a mixture of sand, gelatin, 
salt, and water were to be filtered through cotton wool, 
paper, or other recognised filtering medium, the sand 
would remain on the filter, but the salt and gelatin 
would pass through in solution in the water. It is not 

1 Hober, Arch. ges. Physiol., 1913, 150, 15 ; Moore and Roaf, 
Roll. Zeits., 1913, 13, 133, 


so well known that if such a solution of salt and 
gelatin is placed in a parchment or collodion cup, and 
the latter partially immersed in a vessel of water, the 
salt will pass into the water, but the gelatin will 
remain behind in the cup. By repeatedly changing 
the water in the outer vessel the whole of the salt may 
be removed from the gelatin solution. This distinctive 
property of salt and gelatin was investigated by 
Thomas Graham, who found that all those substances 
which pass readily through a filter, but not through a 
membrane, had certain other resemblances. He also 
found that some substances could exist in such a state 
that they would pass either through a membrane or 
not, according to their method of preparation. Fara- 
day extended this investigation, prepared a number 
of substances in this state, and found that they had 
properties quite different from those ordinarily pos- 
sessed by them. Thus, metallic gold, which is peculiarly 
insoluble and resistant, could be obtained in so fine a 
state of suspension that it passed readily through all 
ordinary filters and behaved as a solution. At the 
same time its colour was entirely different from that 
characteristic of the metal, being red or blue instead 
of yellow, and its other properties were changed to a 
correspondingly great extent. 

When Thomas Graham, in 1861, found that certain 
solutions would pass through a membrane, whilst 
others did not do so, he little realised how great a 
discovery he had made. He had, in fact, found, and 
was able to describe, a state of matter of which little 
or nothing was realised at the time, though many 
industries, and indeed life itself, were and are dependent 


on it. Graham's chief discovery in this connection 
was that substances may enter into solution in such 
a manner that they exhibit characteristics which are 
quite different from those of a true solution. To this 
intermediate state he applied the term " colloidal " 
(from Kolla=g\ue), as glue, gelatin, and allied sub- 
stances were most readily recognised by him as being 
in the colloidal state. Since Graham's time it has been 
found that most substances can be obtained in the 
colloidal state, their occurrence being sometimes due 
to reactions which are specially characteristic of 
animal or vegetable organisms and sometimes to 
purely inorganic changes. 

The colloidal state may be defined as a physical 
condition of matter consisting of at least two parts or 
phases, one of which is the active substance and the 
other the one in which it is distributed. The former 
is termed the disperse phase ; it is the active agent and 
may consist of either solid or liquid particles which are 
so minute that they remain for an indefinitely long 
period in suspension. The second phase is either a 
liquid or an otherwise homogeneous complex material ; 
it is known as the dispersion medium. Such a definition 
does not, however, give any clue to the peculiar pro- 
perties of substances when in the colloidal state, and 
it might be applied with accuracy to any turbid fluid. 
In a colloidal solution which not being a true solution 
is preferably termed a sol the dispersed substance is 
able to react in a manner quite different from what 
would ordinarily be anticipated. The dispersed or 
suspended particles are not merely so minute tHat the 
effect of gravity on them is counterbalanced by other 


forces which keep them in suspension (though they 
are often only one-thousandth part of the size of 
average bacteria), but they are in a state of unordered 
oscillation which gives rise to the well-known Brownian 
movement. They behave in a liquid in a manner very 

a. Hydrogen molecules. b. Chloroform molecules. 

c. Haemoglobin molecules. d?> ,/,' Par tides of colloidal gold. 
h (large circle). Particles which precipitate from gold suspensions. 


(Scale i : 1,000,000) 

similar to the molecules and atoms of a gas, and are in 
constant movement, travelling at a high velocity and 
repeatedly colliding with each other. There is no 
group of substances which are invariably colloids. 
Thus soaps dissolve in alcohol and behave as true 


crystalloids ; in water they behave equally character- 
istically as colloids. Common salt, on the contrary, 
behaves as a colloid in relation to benzole, but as a 
crystalloid when dissolved in water. Von Weimarn 
and others have shown that so many substances can 
be obtained in the form of colloidal solutions that it is 
probably correct to regard colloids as substances which 
are in a particular state rather than as forming a 
distinct group of substances. Colloids are readily 
divisible into two fairly well-defined groups to which 
various names have been given by different investi- 
gators, the most generally accepted being emulsoid 
(fluid particles) and suspensoid (solid particles), as 
suggested by Wo. Ostwald. The colloids in the first 
group have many of the properties of gelatin or glue ; 
they swell when immersed in a suitable fluid (water), 
absorbing a large quantity of it, and gradually become 
so dispersed as to possess many of the properties of a 
solution. The apparently solid particles have many of 
the properties of a liquid, and for this reason the term 
emulsoid is very aptly applied to them. The behaviour 
of emulsoids towards electrolytes is so complex that 
their classification on an adequate, yet simple, scale 
is, at present, impossible. The second group of 
colloids contains substances which are much more 
sensitive to small traces of added substances, and the 
electric charge acquired by them is much greater. 
They appear to consist of extremely minute particles 
of solid matter, though this adjective must not be 
applied too rigidly in this connection. 

There are many well-known organic substances 
which occupy an intermediate position between 


colloids and crystalloids, and are conveniently termed 
semi-colloids. Casein, soap, many degradation pro- 
ducts of albumen, peptones, and other constituents of 
animal organisms, and several dyes belong to this 
class. Thus albumen is a true emulsoid, but the pro- 
talbic and lysalbic acids derived from it diffuse through 
the parchment and behave in other ways as crystal- 
loids, whilst at the same time having several properties 
(such as opalescence, viscosity, and " protective 
action ") which are characteristics of colloids. Semi- 
colloids, such as soaps, may not be colloids under 
ordinary conditions, but form colloidal sols when in 
contact with certain liquids ; they are sometimes 
termed colloidogens. Other semi-colloids are clearly 
electrolytes, but their boiling points and vapour pres- 
sures are approximately the same as those of water ; 
these and other properties are so abnormal that such 
substances must be classed among the semi-colloids. 

Each colloidal particle also carries a characteristic 
definite charge of electricity, some colloids being 
electro-positive and others electro-negative. Usually, 
when any given substance is in the colloidal state it 
has the same electric sign, but by adopting special 
methods of preparation it is possible to produce some 
substances in a colloidal form in which the particles 
may have either a positive or a negative electric 
charge. The electrification of colloidal particles may 
be compared with that of a piece of glass suspended by 
a thin silk thread and rubbed with a piece of amal- 
gamated silk. If a second piece of glass similarly 
electrified by rubbing is brought near to the first there 
will be a mutual repulsion. On the other hand, a 


piece of ebonite which has been rubbed with fur will 
attract the glass because it carries an electric charge 
of the opposite sign. The electric charge is not the 
total amount of electricity which the body possesses, 
but only the excess or deficit of that which it carries 
compared with the neutral electrical condition. 

It is important to note also that the chemical com- 
position, and often the physical appearance of a sub- 
stance, gives no indication of the electric charge which 
it has acquired, so that unless the charge is definitely 
investigated its existence may be overlooked. This has 
to a large extent been the case in the study of many 
drugs and other remedies. 

Substances such as glass and ebonite are most easily 
charged electrically as the result of friction, but this 
is by no means the only or even the most important 
cause of excitation. If two different metals are 
moistened and brought into contact, a feeble but observ- 
able electrification is produced. This is easily shown 
by holding a silver and copper coin edgewise on the 
tongue. So long as the coins are separate no electrifica- 
tion results, but directly they touch each other at some 
point away from the tongue the taste produced by the 
electrification becomes apparent. If two dissimilar 
metals are partially immersed in a liquid which can 
chemically react on one of them, a simple voltaic cell 
or battery unit is formed, the electric current pro- 
duced depending on the sizes of the pieces of metal 
and on the nature of the fluid used. Chemical action 
and electric phenomena are, indeed, so closely related 
that in many instances one cannot occur without the 
other. In fact, many phenomena which are generally 


regarded as chemical are largely electrical in character, 
or at least may be helpfully considered as such. 

For example, the dissociation of a compound into 
its elements or into two distinct groups of ions is 
frequently accompanied by the assumption of definite 
electric charges by each of the groups. Thus, when a 
solution of common salt in water is made sufficiently 
dilute, the salt is dissociated into positively charged 
sodium and negatively charged chlorine particles, or 
ions. Sulphuric acid a more complex substance 
is dissociated into positive hydrogen ions and 
negative SO 4 ions. Even a partial dissociation of the 
fluid in which the substance is dissolved or suspended 
may cause the colloid to acquire an electric charge. 
Thus, water (H + -OH~) can form two classes of colloids 
the particles of which are respectively positively and 
negatively charged, and it is suggested that in many 
cases there is a chemical combination with the liquid 

aPt+H + -OH- = (Pt.H+)+OH-, 

aPb+H+'OH- = (Pb,OH-)+H + . 

The charge on a sol is very much less than on an 
equivalent amount of the corresponding ion, and, 
therefore, a larger amount of sol will be required when 
it is used as a reagent. 

Burton has estimated a charge for a single particle 
of gold and silver sols on the assumption that the 
amount of Al in aluminium salts which just precipi- 
tates the gold or silver has acquired the same amount 
of positive electricity as that amount of negative 
electricity acquired by the precipitated particles. 

The volume of a particle is 2Xio~ 4 cc., so that 


100 cc. of a sol with 6-5 mgms. silver contains 3 x io 10 
particles. This volume of sol required 3-oxio~ 5 
and 2-6xio~ 5 gms. of A1 2 (SO 4 ) 3 for precipitation, 
from which the charge on a particle is 2-8xio~ 2 
electrostatic units, and the charge on one gram-equiva- 
lent of silver in a sol is 4 per cent of the charge on one 
gram-equivalent of silver ion. This dissociation on 
solution with the assumption of an electric charge is 
well known to chemists, though it is not so obvious 
to others on account of the minuteness of the particles 
and of the charges which they carry. There is a 
general agreement among those who have studied the 
subject that colloidal sol particles are enclosed by a 
double electric layer, as suggested by Quincke and 
Helmholtz ; when a particle is negatively charged 
there is a negatively electrified layer on its surface, 
whilst in the liquid immediately surrounding the 
particle is a corresponding layer which is charged 
positively. Burton has shown that there is a layer of 
hydroxide, or hydride, on the colloidal metals which 
may affect the external change on these sols. It is 
not definitely known how this double layer is formed, 
and for most purposes it is sufficient to regard the 
particles as positively or negatively charged, the 
effect of the double layer being neglected. 

Any substance which conducts an electric current, 
and is decomposed thereby into separate groups of 
ions, is known as an electrolyte. The terminals, or 
plates, by which the current is passed through a liquid 
are known as electrodes, the one by which the current 
is supposed to enter being termed the positive (-J-) 
electrode, or anode, and the other, the negative ( ) 


electrode, or kathode. When a current of electricity 
is passed through the solution the positively and 
negatively charged groups tend to collect at the 
opposite ends of the solution, i.e. they tend to travel 
to each electrode respectively, and are in this way 
separated from each other, though they lose their 
characteristic charge as soon as they come into con- 
tact with the electrode. Thus, if a current of electricity 
is passed through water containing sufficient acid to 
render it a conductor, the oxygen atoms will pass to 
the anode and the hydrogen to the kathode, each 
escaping from the solution in the form of a gas without 
any electric charge. Between the electrodes, however, 
the oxygen ions have their distinctive charges and are 
able thereby to act very differently from the electrically 
neutral gases bearing the same names. When a liquid 
is contained in a porous vessel or membrane, which is 
partially immersed in a second liquid, and a current 
is passed from one liquid to the other, the membrane 
plays an important part. It prevents the liquids from 
mixing rapidly, whilst it allows them to come into 
contact with each other, so that by arranging the 
electric current to pass in a suitable direction one sub- 
stance may be passed through the membrane and thus 
separated more rapidly than by the slow process of 
unaided dialysis or diffusion, whilst its separation from 
other substances in solution is effected more easily 
and with less general disturbance than if purely 
chemical methods are used. The chief investigations 
of the movements of colloidal particles under the in- 
fluence of an electric current are based on the work of 


Linder and Picton, 1 who with other observers have 
found that the substances mentioned in Table I 
move to either the positive or the negative electrode, 
as shown, when suspended in pure water. In dilute 
solutions of salts, alkalies, or acids, entirely different 
characteristics may be observed with the same colloidal 

Thus, some colloids such as globulin and silicic acid 
are negatively charged in alkaline solutions and posi- 
tively charged in acid solutions. 




(negatively charged and mov- 
ing to the positive pole) 

Antimony sulphide 
Arsenic sulphide 
Cadmium sulphide 
Platinum sol 
Silver sol 
Gold sol 
Mercury sol 
Silver chloride 
Silver bromide 
Silver iodide 
Vanadic oxide 
Tin oxide 

Aniline blue 

Molybdene blue 
Soluble Prussian blue 

(positively charged and mov- 
ing to the negative pole) 

Hydroxides of 

Iron, Chromium 
Copper, Aluminium 
Zirconium, Cerium 
Bredig sols of 

Bismuth, Lead 
Iron, Copper 
Hoffmann violet 
Magdalene red 
Methyl violet 
Rosaniline hydrochloride 
Bismarck brown 
Methylene blue 
Titanic oxide 

1 Journ. Chem. Soc., 61, 148 ; 87, 63 ; 71, 568 ; 87, 1906. 



(negatively charged and mov- (positively charged and mov- 

ing to the positive pole) ing to the negative pole) 

Fuchsine Diatoms 

Iodine Unicellular algae 

Sulphur Vegetable organisms 

Oil emulsions 
Amoeba? and animal 

The electric charges on gelatin, agar, and silicic acid are 
very small and difficult to observe. 

The rate of movement of a particle in an electric 
field is independent of the size of the particle, but is 
affected by the viscosity of the fluid and the potential 
of the current. 

The employment of electricity remedially for effect- 
ing the movement of the colloidal substances in the 
living cells is, however, extremely limited, especially 
with regard to animal organisms, as a separate elec- 
trode would require to be introduced into each indi- 
vidual cell a hopelessly impracticable condition. 
The result of applying an electric current to a large 
area is entirely different from that which occurs during 
the electrolysis of a single cell. When two sols of the 
same sign are mixed they not only do not precipitate 


each other, but the mixed sol acquires the stability of 
the more stable component. No adequate explanation 
of this fact has yet been published, though the fact 
itself is indisputable. When two particles of opposite 
sign come within a suitable distance of each other they 
are mutually attracted and, if sufficiently free, will 
eventually touch and discharge each other. The 
product will then be electrically neutral unless one of 
the particles carries a larger charge than the other, 
when the product will carry the balance of the charge 
or will decompose, forming an electrically neutral 
substance which settles more or less rapidly and a 
negatively charged product. 

Substances in the colloidal sol state have correspond- 
ing electric charges and therein bear a very close 
resemblance to substances which become ionised in 
solution. They attract particles of opposite sign and 
repel those of like sign which come within the sphere 
of their influence, and when two colloidal sol particles 
of opposite sign come into contact with each other 
they are mutually discharged, and the combined pro- 
duct settles more or less rapidly. Thus, the effect of 
discharging two colloidal sol particles is to remove 
them from the active colloidal state and to form a 
precipitate or even a coagulum. This may, under some 
conditions, retain a certain amount of chemical 
activity, and being then in an intermediate state 
between a sol and a precipitate is conveniently known 
as a gel. Gels are usually obtained when emulsoid sols 
are cooled or evaporated ; they may be regarded as 
composed of two liquid phases, whereas a sol bears a 
closer resemblance to a solid phase dispersed in a liquid 


one. Gels have characteristic optical properties, such 
as double refraction. 

Agglutination, or the precipitation of colloids of like 
sign, occurs in some cases, e.g. with toxins and bacteria 
sols. Though extensively used by some pathologists 
as the basis of treatment of diseases due to toxins, 
bacteria, etc., the precise nature of the phenomena 
which produce agglutination are by no means well 
understood. Lottermoser, in 1901, found that when a 
positive sol precipitates a negative one, the precipitate 
contains both colloids. 

The amount of one sol required to precipitate 
another varies with the nature of the sols, and the 
precipitate contains both colloids, though, owing to 
the difficulty of nitration without adsorption, the 
liability of the excess of colloid in the sol to precipitate, 
and the slowness of the reaction, it is often difficult 
to determine the amount of each colloid in a precipitate. 

The equivalent amount of sols required to cause 
precipitation is not a chemical equivalent, but an 
electrical one ; usually the maximum precipitation 
occurs when the positive charge on one cell exactly 
equals the negative charge on the other, but the 
number of particles, their size, and the rate of mixing 
affect the results. 

Substances in colloidal solution behave quite differ- 
ently from those which are merely in suspension. 
Thus, coarse suspensions are not affected by electro- 
lytes and they do not usually bear a definite electric 
charge, whereas colloidal sols unless protected are 
very sensitive even to traces of electrolytes, and 
readily migrate towards one pole when an electric 


current is passed through them. It is a mistake to 
regard them merely as fine suspensions, as the proper- 
ties of a substance undergo considerable change when 
it is converted into the sol state. They do not behave 
precisely the same as either suspensions or solutions, 
but occupy an intermediate position for which the 
term " sol " is preferable. It was at one time thought 
that colloidal substances could be defined as those 
which appeared to be in suspension but do not pass 
through a parchment or collodion membrane into an 
external volume of water. This is by no means always 
the case, as Graham soon found, and since his time 
more anomalies have been discovered. It is scarcely 
possible, therefore, in simple terms to say precisely 
which substances are colloidal and which are not, 
though for most practical purposes the distinction is 
readily appreciated. Like " life/' we may have a fairly 
clear concept, but cannot express it in mere words. 

The difficulty of finding a clear line of demarcation 
between colloidal and other substances is greatly 
intensified when living organisms are studied, as 
reactions take place in these which do not occur in the 
dead organism. For example, the peptones are a 
class of nutritive substances which are in many 
respects typically colloidal, and in the laboratory 
their solutions do not pass through animal or vegetable 
membranes. In the living organism, on the contrary, 
peptone solutions pass readily through certain mem- 
branes and owe their nutritive power to this property. 
Haematin, on the other hand, is a typical crystalloid 
substance which might be expected to pass readily 
through the blood vessels, yet it does not do so as 


long as the organism is alive. Here are two typical 
substances, both acting precisely contrary to the 
general behaviour of the groups to which they belong, 
whilst in the living organism, but behaving normally 
when removed from the organism and studied in vitro. 
This difference in behaviour impels all investigators 
who are aware of it to pause ere they draw conclusions 
from laboratory experiments and apply them to the 
living subject. Even in so apparently simple a 
phenomenon as the passage of a substance through a 
membrane, the effect of "life" may be to upset all 
prognostications from the tests on dead or synthetic 
materials. This fact needs specially to be borne in 
mind when dealing with the introduction of drugs and 
other substances into the living subject, or seriously 
erroneous conclusions may be drawn. 

Turning again to the characteristics of colloidal 
substances, it should be observed that they are most 
remarkably active, an apparently minute proportion 
of a suitable colloid frequently effecting the precipita- 
tion of many times its weight of another substance 
from " solution." In this respect, many colloids re- 
semble enzymes, or so-called vegetable ferments, and 
bacteria, though they do not reproduce themselves 
like living organisms. They owe their activity to 
their minuteness and to the fact that substances when 
in the colloidal state have an enormous surface area 
as compared with their volume or weight, and as 
chemical reactions depend on the amount of contact 
between two or more particles these reactions will 
proceed the more rapidly and completely when the 
substances have a large surface area and are in a state 


of oscillation. It is well known that chemical reactions 
can only occur when two or more substances are in 
direct contact, and as the completeness of the reaction 
depends on the amount of contact, colloidal substances 
are very powerful because of the enormous area they 

On the other hand, mass plays an important part 
in all chemical reactions and largely regulates their 
intensity. The mass of colloidal sol particles is so 
minute that the objectionable effect of intense reactions 
on the human subject are largely avoided, whilst the 
advantages of rapid and complete reaction are secured. 
For this reason, certain medicines administered in the 
colloidal form are not merely more active and possess 
greater penetrating power, but they are free from the 
poisonous effect of the same substances when given in 
the form of tincture or solution. The difference in 
behaviour of a solution of iodine in alcohol or aqueous 
potassium iodide, when compared with that of colloidal 
sol iodine, is most impressive. The forms of iodine 
usually employed induce pain and other symptoms of 
iodism, whereas large doses of colloidal sol iodine (if 
the preparation has been properly prepared) are quite 
free from this risk. A colloidal preparation of iodine 
in petroleum or other mineral oil can be rubbed into 
the skin without leaving any stain, the iodine being 
absorbed more readily than the oil. A solution of 
commercial iodine in alcohol or in potassium iodide 
leaves a characteristic stain when applied to the 

The precise reason for this rapid absorption and 
non-staining action has not been definitely ascertained, 


but it has been repeatedly demonstrated in a variety 
of cases. 

The action of radiations on sols. The y-rays of 
radium and the X-rays have no action on colloidal 
sols. The positively charged a-rays of radium have 
not sufficient penetrating power for any action they 
may have to be important. The /3-rays of radium, 
which are negatively charged, hasten the coagulation 
of the positively charged particles and increase the 
stability of the negatively charged ones. A sample of 
haemoglobin was coagulated by the rays in several 
hours by Hewin and May en. 1 Some albumen sols 
when exposed to the ultra-violet light are rapidly 
coagulated. These reactions partially explain some of 
the remedial effects of various radiations on the human 
system. It is clear that such effects are limited by the 
permeability of the skin, and that for deep-seated 
affections better results may be anticipated from the 
introduction of suitably charged particles (colloidal 
sols) into the blood stream. 

The colour of colloids. The colour of the colloids 
depends chiefly on the size of the particles, and only 
to a small extent on their composition. Thus, the 
smallest particles of colloidal gold, when seen by 
transmitted light, are red and the larger ones are blue. 2 
The colour is, in each case, dependent chiefly on the 
scattering effect of the particles on the light trans- 
mitted through the liquid. In accordance with 
Rayleigh's & Thompson's calculations, the intensity 

1 CR., 138, 1904, 521 ; CR. Soc. de Biol, 57, 1904, 33. 
* Mee found the relation of the size to colour reversed in some 


of the scattered light varies directly as the sixth power 
of the diameter of the particles and inversely as the 
fourth power of the wave-length. Hence, the intensity 
of the scattered light and the absorption are both 
greatest with the smallest particles. Stebbing found 
that very little light leaves a colloidal liquid, most of 
it being absorbed. Svedberg found that colloidal sols 
are often more highly coloured than a true solution of 
the same element at the same concentration, but that 
the absorption spectra of the colloidal sols and solu- 
tions do not differ essentially. W. Ostwald l has 
enunciated the law that " with decreasing size of the 
particles the absorption band of any colloidal solution 
moves to the shorter wave-lengths." 

Mayer, Schaffer, and Terroine 2 have shown that 
traces of alkali increase the size of the particles if the 
colloid is positive, and reduce it if the colloid is negative. 
Traces of acid produce the reverse effect. The change 
in the dispersion thus effected varies with the colour of 
the sols. Zsigmondy 3 and Gutbier and Resenschack 4 
found that, on adding coagulating reagents, the colour of 
gold sols changes consecutively from red to purple-red, 
red- violet, blue- violet, and deep blue, the colloid 
eventually separating as flakes of powder or gel. 

1 Roll. Chem. Beiheft., 2, 1910 ; n, 409. 

2 Comptes r endues, 1907, 145, 918. 

3 Zier, Erkentniss der Koll. 

4 Z.f. anorg. Chem., 1904, 39, 112. 



THAT animal and vegetable fluids are largely colloidal 
in character is a fact which is now unquestioned, but 
little is known as to their precise nature. Thus, the 
particles in cow's milk can be demonstrated under the 
ultra-microscope, but those in human milk are too 
minute. This suggests that in adapting cow's milk 
for feeding infants, it is not sufficient to endeavour to 
match the ordinary chemical analysis of human milk, 
but that cow's milk should be treated in such a manner 
that the product is in a similar colloidal state to that 
of the human milk. The valuable superiority for 
infant use of milk to which barley water, gruel, or 
other starchy solution has been added has long been 
known, but few have, as yet, realised that it is due to 
the protective action (in a colloidal sense) of the added 
substance. Gelatin, gum-arabic, or preferably gum- 
acacia, have an even stronger protective action, and 
they possess the further advantages of being easier to 
prepare and of altering the composition of the milk to 
a less extent, whilst making it physically much more 
like human milk. 

In human milk the protective colloid is lact-albumen, 
which is present to the extent of 1-3 per cent (i.e. equal 
to the casein present), whilst cow's milk contains only 
0-5 per cent of lact-albumen and over 3 per cent of 



casein. Of all the domestic animals, asses' milk bears 
the closest resemblance to human milk, both in 
chemical and colloidal properties. 

The coarse particles of curd which are formed when 
cow's milk is coagulated by acids or rennet may be 
replaced by finer, more flaky, and more porous curds 
by diluting the milk with water, by adding lime-water 
(though this tends to prevent the coagulation altogether 
and so may unduly delay its digestion or even cause it 
to be passed out of the body of an infant in the un- 
digested state), and by the use of one of the protective 
colloids previously mentioned. 

Bearing in mind its colloidal nature, human milk 
can best be imitated by using cow's milk as the basis 
and adding the following : (a) cream sufficient to 
raise the total fat present to 3-8 per cent (about 3 per 
cent of the final mixture being required usually) ; 
(b) milk sugar to raise the total sugar content to 
6-2 per cent (about 3 per cent of the total mixture 
being usually required) ; (c) about I per cent of lact- 
albumen, or 2 per cent of gelatin, or a considerably 
larger percentage of starch in the form of barley water, 
etc., as the protective colloid ; and (d) sufficient 
water to effect the solution of the protective colloid 
and the sugar. If there is any risk of the cow's milk 
not being quite fresh, part of the added water may 
wisely be replaced by a tablespoonful of lime-water, 
which will neutralise any trace of acidity in the milk 
and will therefore increase its keeping power. 

In the same way chemical analysis alone does not 
determine the value of even the essential properties 
of a foodstuff ; its physical condition particularly 


if it is a colloidal substance is of at least equal and 
sometimes greater importance. Thus, cheese cannot 
be digested by some people as it is too densely coagu- 
lated to be readily converted into a colloidal fluid. 
By preparing it under conditions which will facilitate 
its resuspension, its high value as a food material may 
be utilised. The various preparations of casein which 
are at present so popular as recuperatives depend 
largely on the fact that they are colloidal substances, 
which can be resuspended or converted into colloidal 
fluids more easily than ordinary cheese or dried milk. 
Indeed, the chief test of such a preparation may 
usefully consist in an examination of its properties 
when mixed with water or other suitable fluid. 

The cell-structure of animal and vegetable organisms 
closely resembles the cellular structure of the synthetic 
cells. The walls of such cell-structures are really 
emulsoid gels, the cell-fluid being an emulsoid sol. 
The gels which form the cell-walls and membranes of 
the body contain albumen- and gelatin-like substances 
which swell in water and to a varying degree in solu- 
tions of acids, alkalies, and salts. In other words, 
living protoplasm is essentially a complex liquid ; the 
presence of a network, observed in protoplasm which 
has been killed or " fixed " by various reagents, is 
not apparently seen in the living material. The so- 
called cell-wall of the protoplasm of some low forms 
of life appears to have both the properties of a solid 
and of a liquid substance, and in this respect resembles 
the film of a soap bubble. For example, Chambers has 
recently (1917) found that a needle can be repeatedly 
passed into living protoplasm without injuring it 


in any way and without leaving any trace of its track. 
Bacteria, etc., penetrate the cell- wall in a similar 
manner without damaging it, just as well as through a 
soap-bubble. The outer layer of protoplasm is not, 
however, identical with the membrane to which the 
cells owe their semi-permeable properties. 

When a cell dies it passes from an emulsoid sol into 
an emulsoid gel state and thereby changes its character 
and reactions, one of the most remarkable differences 
being that the liquid of the dead cell freely mixes with 
the surrounding watery solution, whilst the contents 
of the living cell do not escape in this manner. Under 
normal conditions living cells are non-conductors and 
are largely impermeable, but under the influence of 
certain ions they become permeable and allow electri- 
cally charged particles to pass freely through them. 
When certain cells are immersed in a saline solution 
the sodium ions present increase their permeability ; 
the addition of calcium ions restores them to their 
normal condition. Hence simple solutions of salts do 
not form an efficient substitute for the blood or for 
the sea-water in which marine creatures live ; a small 
but significant proportion of calcium salts is essential 
unless a colloid, such as gelatin or gum-acacia, is added 
in sufficient proportion to give the saline solution an 
osmotic pressure as high as that of the blood. The 
selective permeability of living cells is very remarkable. 
Acids which are soluble in the cell or in the analogous 
liquid bodies readily penetrate the cells, but other 
acids and strong bases do not. Weak bases (including 
ammonia and the amines) penetrate the cells without 


Although sodium hydroxide does not enter the 
living cells it greatly increases the rate of oxidation 
processes in the cells. This is due to the fact that the 
cell-wall is really a concentration of the components 
of the protoplasm of the cell, and in the presence of 
sodium hydroxide the normal equilibrium is upset, 
and this produces marked changes in the cell, not- 
withstanding the fact that the sodium hydroxide 
does not penetrate into it. 

The cell materials, whilst being typical emulsoids, 
behave in a far more complex manner than the syn- 
thetic emulsoid gels or the natural or synthetic sus- 
pension sols. Thus, albumen is electrically neutral and 
is precipitated by basic emulsoids (as histone) and 
basic sols, which are positive sols. It is also precipitated 
by acid emulsoids, such as silica sol and acid dyes, 
which are negative sols. Tannin and gallic acid behave 
similarly. Perrin l has suggested that primary cell 
growth and cell division are essentially colloidal in 
nature, an idea which is, to some extent, supported by 
galvanotropism in microscopic animals. 2 If this is the 
case and there is much evidence in support of it a 
study of the changes in the viscosity of the body fluids 
under certain circumstances, 3 the influence of certain 
salts on the properties and action of the blood, 4 and 
the laws regulating the permeability of the cell-walls 
for salts and colloids in the human body are bound to 

1 Journ. Chim. Phys., 1904, II, 607. 

8 Miller, Journ. of Physiol., 1907, 215. Buxton and Rahe, Zs. /, 
D. Ges., Bischam, XI, n to 12, p. 479. 

8 Rachlmann, Bert. kin. Wochensch, 1904, Heft. 8 ; Deutsche 
Med. Wochensch, 1904, Heft. 29. 

* Nanes, Chem. Beih. Physiol., 1910, 40, 327. 


advance our knowledge of the normal action of the 
body and to increase our power of treatment when it 
is diseased. As an instance of the advance which has 
been made since the colloidal nature of animal and 
vegetable substances has been appreciated, it may be 
noted that when investigating albumens and their 
digestive products, students of physiological chemistry 
have long been puzzled by the complexity of the 
mixtures precipitated by various reagents, such as 
ammonium or zinc sulphate. It has been impossible 
to effect really satisfactory separations of such sub- 
stances by ordinary chemical processes, but their 
strikingly different behaviour towards colloidal metals 
has opened out a new field of research which it is 
anticipated will have far-reaching results. Another 
interesting result of the recognition of the colloidal 
nature of blood may suitably be mentioned here. 
For many years it has been held that the oxygen in 
the blood was in the form of a compound of oxygen 
and haemoglobin, but in 1907 Wolfgang Ostwald 
pointed out that all the available data may be arranged 
to form graphs or curves which are typical of adsorption 
and there can be little tfoubt that both the oxygen and 
the carbon dioxide in the blood are in an adsorbed 

Red blood - corpuscles are negative, but can be 
precipitated by both positive and negative sols. 
Henri l assumes that they are surrounded by a pellicle 
which can adsorb salts, such as magnesium and 
calcium sulphate. These salts act on any precipitable 
sol, producing a coagulum around the corpuscles ; 

1 Compt. Rend., 1904, 138, 1461. 


they can be removed by diffusion into an isotonic 
sugar solution, after which blood-corpuscles are much 
less susceptible to precipitation by sols. 

Blood-corpuscles which have been soaked in solu- 
tions of salts especially chlorides and sulphates are 
made more easily precipitable by sols, especially ferric 
hydroxide sol. 

The fact that the blood is a typical complex 
colloidal fluid is now accepted, and this is the basis 
of the treatment of numerous diseases, though many 
physicians have scarcely recognised it. The colour- 
ing matter hczmoglobin is definitely colloidal, and 
hence it is not surprising that the colouring matter 
obtained from different animals differs both in its 
composition and properties. In red corpuscles from 
the human subject, the haemoglobin is associated with 
a complex of various substances, some colloidal and 
others crystalloidal, and with a liquid which is isotonic 
with a solution of nine parts of common salt in a 
million parts of water. If the red corpuscles are 
immersed in a more dilute solution than this they 
swell, and haemoglobin gradually passes from them to 
the external solution (hczmolysis). The importance 
of this phenomena which is characteristic of colloidal 
gels will be appreciated when considering the effect 
of colloidal substances in diseased conditions of the 
human subject. 

The characteristic behaviour of some of the waste 
products of the human organism is also due to their 
colloidal character. Thus, urine contains colloidal 
substances which normally prevent the uric acid from 
separating. This colloid may be removed by dialysis 


or precipitated by alcohol ; it appears to be a deriva- 
tive of nucleinic acid. Urines which are deficient in 
this protective colloid may be prevented from deposit- 
ing uric acid on cooling by adding to them a suitable 
colloid. Unfortunately, those colloids, such as gelatin, 
which are most successful in vitro, are absorbed by the 
alimentary tract and therefore do not reach the 
bladder in sufficient quantity to admit of their being 
used in certain urinary diseases. Experiments with 
other colloids are now being made. In this connection, 
it should be noted that alcohol reduces the rate of 
diffusion of salts in gels, whilst urea, chlorides, and 
iodides increase it. 



THE important part played by colloidal sols and gels 
in the maintenance of hygienic conditions is seldom 
realised by those whose attention has not been called 
to this aspect of the subject. The removal of harmful 
impurities in water, the disposal of sewage in an in- 
nocuous manner, and the effective disposal of " dirt " 
are all largely dependent on some colloidal properties, 
the precise nature of which is by no means well recog- 
nised by many of those engaged in the purification of 
water, or sewage, or who are habitual users of soap and 
other detergents. 

The study of colloids in relation to these subjects is 
comparatively new, and much has yet to be learned. 
On the other hand, it is interesting to note how much 
of the best modern practice and use of colloidal pro- 
perties has been reached by persistent investigation 
on the lines which had little or no bearing on the 
recognition of the real nature of colloids. Now that 
the importance of the colloidal state has been recog- 
nised in other branches of industry and science, it is 
surely not too much to hope that it will lead to equally 
striking improvements in the sphere of hygiene. A 
few words on each of the important subjects of sewage, 
water, and soaps must, however, suffice. 

Sewage. Sewage consists essentially of water con- 


laminated with excrement, kitchen- and other domestic 
refuse, and matter washed from roads ; in some areas 
it may be further contaminated with other waste 
products from factories, or other industries. This 
contaminated matter is in three forms : (a) in sus- 
pension, as silt, sand, paper, rags, faeces, vegetable and 
animal matter, etc. ; (b) colloidal matter in solution 
or pseudo-solution ; and (c) in true solution. In 
purifying sewage the chief purpose is to separate the 
matter in suspension and to render harmless that in 
colloidal and in true solution. The chief difficulty in 
dealing with sewage is that the matter in colloidal 
solution prevents the effective removal of the coarse 
material in suspension, as well as assisting in keeping 
it in suspension in larger proportions than would 
otherwise be the case. Hence, if the colloidal matter 
can be precipitated in a suitable form the most serious 
difficulty in sewage treatment is overcome. 

The complex nature of sewage is such that it is 
impossible to treat each of its constituents separately, 
and this adds to the difficulty of purification. It is, 
however, recognised that the most difficult constituents 
are the colloidal sols, and these can be precipitated 
in accordance with the recognised methods for pre- 
cipitating other colloids. The most successful chemical 
methods of treatment depend on a recognition of this 
colloidal character and on the coagulation of the 
colloidal sol by the addition of some other substance 
carrying an electric charge of the opposite sign. Ferric 
and aluminium hydroxides have been largely used for 
this purpose, and they are quite efficient. Their great 
drawback is the cost of treating such enormous volumes 


of liquid by any process of sedimentation and filtration 
to remove the precipitated colloid and the difficulty 
hitherto experienced in converting this colloid into a 
useful material. The method which appears most 
likely to prove of value consists in utilising the fact 
that water which has been violently agitated with, or 
has fallen through, air may become positively charged, 
and these electrically positive particles then effect the 
coagulation of the negatively charged colloids in the 
sewage. Hence, by agitating the sewage with air, 
under suitable conditions, a complete coagulation of 
its colloidal content is rapidly effected at a low cost, 
and the precipitate is one which settles with extra- 
ordinary rapidity. In the well-known " activated 
sludge " process, air is blown through the sewage, the 
inventors of this process having apparently failed to 
realise that the electric charge of the water particles 
is at least equally as important as the oxidising power 
of the air. A modification of this process, in which 
the water is charged positively by agitating it super- 
ficially with air, offers still greater prospects of success, 
as it avoids the use of " chemicals " and the costly 
supply of large quantities of air. In this connection it 
is interesting to note that beneficial action of the air 
at the seaside is probably due more to the particles in 
it which have been positively charged by the violent 
beating of the waves on the -shore, than to the ozone 
to which this action is usually attributed. These 
positively charged particles, reacting with the nega- 
tively charged bacterial and other undesirable colloids, 
precipitate them and render them harmless. 

The purification of sewage is complicated by the fact 


that the precipitation of the colloidal and suspended 
material is not sufficient to remove all the putrefactive 
constituents : though the greater part is so removed. 
The remainder appears to be most advantageously 
treated by bacterial action, especially by the activated 
sludge, or similar process, and, as it happens, the two 
processes of precipitation of the colloids and the 
development of bacterial action can in most cases be 
carried on simultaneously. The action of bacteria 
alone (as in a septic tank) does not appear to affect 
the proportion of colloidal matter to any serious 
extent, so that where the purification is confined to 
bacterial treatment the precipitation is more prolonged, 
and the final purification of the liquid is much less 
complete than when the colloids are precipitated in 
the presence of, or prior to, the action of the putrefying 

The sludge produced by the precipitation of the 
colloidal matter by electrically charged air, with or 
without the action of the activated sludge, is a fairly 
stiff material which settles rapidly and is easily 
filtered, whereas the ordinary sewage sludge is largely 
liquid. The sludge may suitably be subjected to 
anaerobic bacterial action, whereby it is converted into 
a more dense and granular material which is free from 
the objectionable qualities of the untreated sludge. 

The purification of water. The artificial purifica- 
tion of water is effected by colloids : 

(1) A colloidal coating on the grains of sand in the 
filter retains (by neutralising the charge) all the 
bacteria, etc., but not the colouring matter. 

(2) Aluminium sulphate, or ferric sulphate (with or 


without alkali), is added to the water, and causes a 
precipitation of the positively charged alumina, or 
ferric oxide, which reacts with the negatively charged 
bacteria, clay, etc., and precipitates them. Simultane- 
ously, the positively charged colouring matter is pre- 
cipitated by the negatively charged SO 4 ions, whilst 
any true colouring matter is adsorbed by the precipi- 
tated hydroxides. Any excess of alumina, or ferric 
oxide, is precipitated by agitation. 

Sometimes it is best to add the alkali first ; some- 
times only after the aluminium or ferric sulphate. 
The latter is preferable when there is much colouring 
matter to be removed. 

The natural purification of muddy water is largely 
dependent on its colloidal character. Thus Skey l 
has shown that suspended mud is precipitated by 
electrolytes, including those in sea water. Hence, 
when a muddy river flows into the sea the proportion 
of mud which settles out, owing to the slower current 
in the mixed water, is insignificant compared with 
that which is precipitated by the electrolytes in the 
salt water. Schloesing 2 has shown that deltas are 
chiefly due to this cause. 

Soaps. Sir Edwin Chadwick was a firm believer in 
the idea that the effectual preventative of all forms of 
epidemic, endemic, and most other diseases, is the 
entire removal of all conditions of dirt, including foul 
air, defective drainage, and dirty surfaces of all kinds. 
He was most emphatic as to the necessity of personal 
cleanliness, and on one occasion he declared that if a 

1 Ghent. News, 1868, 17, 160. 

2 Journ. Chem. Soc., 1874, 30, 37. 


great epidemic were to occur he would proclaim and 
enforce the active application of soap and water as 
the chief preventative. In any consideration of the 
subject of colloids in relation to health and disease, 
under the auspices of the Chadwick Trustees, it is, 
therefore, desirable to point out that the detergent 
action of soap to which Chadwick and his colleagues 
attached such importance is almost wholly due to its 
colloidal character, by means of which it is able to 
reduce the surface tension between other solids 
(" dirt ") and water, and to effect the removal of the 
former by a process of colloidal solution. It is a 
striking fact that a i per cent solution of soap will 
reduce soot to so fine a state of subdivision that it will 
pass completely through any filter, and will remain 
suspended indefinitely. In a 2 per cent solution of 
soap, on the contrary, the soot will be deposited 
almost as rapidly from pure water ! In a similar 
manner a solution of soap in water will " disperse," or 
bring into " colloidal solution," a sufficient proportion 
of " dirt " adherent to any cleansable surface to enable 
the whole of the " dirt " to be removed in suspension 
in the fluid. The addition of any abrasive or scouring 
material such as finely ground sand or silica flour 
may aid the cleansing process, but the chief feature of 
it is, nevertheless, the production of a colloidal solution 
of a sufficient proportion of the " dirt " to enable the 
remainder to be removed readily. 

The peculiar behaviour of soap has puzzled many 
investigators, some of whom have doubted its colloidal 
character yet have failed to find a complete explanation 
in a purely chemical conception. The true nature of 


soap is most probably shown by Bancroft, who has 
suggested that undissociated soap appears to be almost 
wholly present in colloidal form, but in the presence 
of water the sodium palmitate, or corresponding com- 
pound, is hydrolised, the OH ions being largely 
adsorbed by the undissociated soap, the adsorbing 
substance then becoming an anion. 



THE microbic origin of many communicable diseases 
is now generally recognised, and it is reasonable to 
presume a similar cause in many other diseases with 
which no specific micro-organism has been identified. 
Many of the disease-producing bacteria are sufficiently 
large to be readily visible under a powerful micro- 
scope, but others, such as those relating to yellow 
fever, foot-and-mouth disease, and tobacco disease, 
are too small to be directly visible. Their existence 
has been discovered indirectly by means of the 
ultra-microscope an instrument which is described 

Whilst recognising the remarkable advances in the 
treatment of many diseases which have resulted from 
the recognition of their bacterial or protozoal origin, 
the fact still remains that by far the most marvellous 
preventatives of disease are contained within a normal, 
healthy body, in which, as Lister has clearly demon- 
strated, bacteria can only establish themselves when 
conditions have arisen which create a state of un- 

The period in which all zymotic diseases were 
attributed solely to the introduction of bacteria, or 
protozoa, into the otherwise healthy subject is, 
happily, passing away, and pathologists and others 



are increasingly recognising as a fact the necessity for 
the bodily conditions being suitable before the disease 
germs can multiply extensively in it. As a result of 
the wide recognition of this fact originally pointed 
out, though expressed in different terms, by Sir Edwin 
Chadwick and his colleagues it is now seen that 
attention should be concentrated on the state of the 
body fluids and cells as well as on the invading micro- 
organisms. Now that the colloidal nature of the body 
fluids and cells has been recognised, it is possible to 
make considerable progress in maintaining them in, 
or restoring them to, a suitable condition on purely 
chemical or physio-chemical lines. The subject is too 
vast to discuss in detail in the present volume, but 
briefly it is now admitted that if the normal colloidal 
condition of any of the more important body fluids, or 
cells, is disturbed by the advent of undesirable electro- 
lytes, salts, or colloids of the " opposite " sign, condi- 
tions are produced which provide a suitable nutrient 
medium for many of the disease-producing germs which 
are constantly coming into contact with the body. If 
the altered body fluids or cells can be restored to their 
normal colloidal state without seriously damaging 
any other portion of the subject, the invading germs 
will soon perish and will be removed from the body 
by the normal processes of life. If this view of the 
matter is correct, it is of far greater importance to 
restore the disarranged colloidal state to its normal 
condition than it is to endeavour to kill the invading 
germs without otherwise altering the state of the 
diseased or altered cells or body fluids. In the latter 
event it will only be a question of time before the 


patient is attacked by further organisms, and these 
attacks will be continued until, by some means or other, 
the diseased organs regain their normal colloidal state, 
or until they are atrophied or have been removed by 
means of a surgical operation. If, on the contrary, 
the normal colloidal state of the diseased organ can 
be restored, the body as a whole is well able to effect 
a complete recovery without any serious risk or delay. 
The importance of the influence of the " soil " upon 
the " seed," and the predisposition of the individual 
body to attacks by germs, has been established by 
Sir Wm. Collins in an essay published in 1884, 
dedicated to Herbert Spencer, who " regarded it as 
opening the way to a considerable reform in pathology." 
If his theory (as to underestimated influence of evolu- 
tion on the specific disease-producing effects of or- 
ganisms whose cycle may be only a few hours or even 
less than one hour, and whose rate of propagation is 
incalculable) is approximately correct the necessity of 
maintaining the body fluids in the correct colloidal 
state must be obvious. The rational treatment of 
zymotic disease must not depend solely on the destruc- 
tion of the germs by means of which the disease is 
propagated ; the requisite attention must also be 
paid to the " soil," or medium, in which the germs 
exist in the body. 

This is readily understood when it is realised that 
emulsions of bacteria may be regarded as suspensoids 
protected by an emulsoid sol. They are precipitated 
by definite amounts of electrolytes, such as acids, 
heavy metal ions, and by aluminium and ferric ions, 
as are ordinary suspensions. Emulsions of bacteria 


are not precipitated by alkalies and are not protected 
from precipitation by other emulsoids, such as gelatin, 
as are many negative colloids. The addition of an 
immune serum to a bacteria sol greatly increases 
the sensitiveness of the latter to electrolytes, and 
apparently destroys the protecting part of the bacteria 
sol, which thus becomes a suspensoid sol. 

Unfortunately, the colloidal characteristics of fluids 
containing bacteria are highly complex. Many of their 
reactions appear to be partly of a colloidal and partly 
of a chemical nature. Thus, the reaction between 
bacteria and agglutinins, including emulsin and gelatin, 
resembles an adsorption, but as sols of any one kind of 
bacteria are affected only by the agglutinin produced in 
the serum by the injection into the animal of the same 
kind of bacteria, this fact seems to imply the existence 
of definite chemical properties. On the other hand 
some bacteria sols are definitely affected by inorganic 
colloids in a manner which suggests both a colloidal and 
a chemical action. 

Toxins and anti-toxins. Toxins are the products of 
bacterial life, and are to some extent analogous to the 
excreta of the higher organisms. They are decom- 
posed and rendered harmless by a number of sub- 
stances, of which special interest attaches to those 
other products of bacterial life (such as immune serum) 
known as anti-toxins. Thus, when a suitable immune 
serum is added to the corresponding bacteria sol, 
the latter does not coagulate, even after dialysis, but 
it becomes so sensitive to electrolytes that the latter 
coagulate it easily. This is explained by the suggestion 
that the agglutinin in the serum destroys a protecting 


agent which is assumed to be present in the bacteria 

A mixture of the corresponding agglutinin and 
bacteria sol is not precipitated by OH ions, but 
readily so by acids and salts of the heavy metals. 
The addition of salts precipitates the colloids if there 
is an equivalent of agglutinin to bacteria sol. If either 
colloid is greatly in excess of the other no precipitation 

Both toxins and anti-toxins are colloidal, particu- 
larly the latter. Thus, when a diphtheria toxin is treated 
with its anti-toxin, the reduction in toxicity depends on 
the manner of administration. If the anti-toxin is 
added in small quantities at long intervals much more 
anti-toxin is needed. 

Field and Teague 1 found that both toxin and anti- 
toxin migrate distinctly in an electric field. There 
may be a chemical compound between the toxin and 
the anti-toxin, but more probably there is a mutual 
adsorption, the reaction being wholly colloidal. A 
difficulty exists with both explanations, inasmuch as 
diphtheric anti-toxin is the only one which will neu- 
tralise the diphtheria toxin, and, at present, both 
these substances appear to possess both chemical and 
colloidal properties. 

In addition to the difficulty of treating such com- 
plex substances in accordance with general principles, 
there is the further disadvantage that, whilst blood 
serum has normally a positive charge, most of the sols 
of the pathogenic bacteria are not coagulated by fluids 
with such a charge. This remarkable behaviour may 

1 Journ. Exp. Med., IX, 86. 


be due in part to the presence of a powerful protecting 
agent, but if this is correct it only transfers the diffi- 
culty without eliminating it. The value of a suitable 
immune serum lies in its power of increasing the 
sensitiveness of the bacteria sols to electrolytes, and 
thus facilitating their precipitation. Much work is 
now being done in the endeavour to ascertain the 
chemical or colloidal nature of the various agglutinins, 
and until the results of this work have been published 
judgment on this matter must be deferred. The fact 
that so small a quantity of the agglutinins has such 
far-reaching effects is highly confirmatory of their 
essentially colloidal character, and their peculiar 
specificity may ultimately be found to be due to the 
simultaneous production by the bacteria of a specific 
protecting agent which, in its turn, may be decomposed 
by the elementary colloidal sols, though it resists the 
attack of compound sols. 1 

1 Further information on the current views of the reactions 
between agglutinins and bacteria will be found in : 

Immuno-chemistry, S. Arrhenius (Macmillan and Co.). 

Le mechanisms de V agglutination, J. Bordet. Annales de VInst, 
Pasteur, 13, pp. 225 to 272. 

" Mechanism of the Agglutination of Bacteria by Specific Sera," 
W. J. Tulloch, Biochem. Journ., 8, pp. 294-319. 



THE similarity between the poisoning of animals and 
the stoppage of the reaction of certain metallic sols by 
small quantities of well-known poisons is very striking. 
Thus, the presence of a trace of prussic acid will reduce 
the speed of reaction of platinum sol on hydrogen per- 
oxide to half the normal rate, and a somewhat larger 
proportion will cause the reaction to cease. Enzymes 
and ferments are " poisoned " in a similar manner. 

This great similarity between animal "poisoning" 
and a stoppage of a relatively simple chemical reaction 
is very important, as it suggests many other points of 
possible resemblance which are worth further study 
and opens out large fields of chemical research in 
connection with biological and physiological problems. 
Moreover, the relative ease with which the effect of 
metal and other sols on chemical reactions can be 
studied and controlled, suggests that similar reactions 
equally well controlled may be effected in the 
human subject with far-reaching results. 

Digestion and colloids. The reactions which occur 
in normal digestion result in the production of sub- 
stances which are able to pass through the membrane 
of the alimentary canal into the blood stream. At the 
first glance, it may be supposed that such a passage 
would exclude all colloidal sols, though precisely the 



opposite is the case. It has been found that in the 
presence of a crystalloid, such as common salt, the 
passage of colloidal sols through the membranes is 
considerably increased, thus showing the importance 
of the salt to the animal and human organism. The 
advisability of eating salt with so typical a colloidal 
gel as a boiled egg is thus seen to be based on a physi- 
ological requirement, and not merely on a matter of 

It is important to observe that the products of 
digestion, and some other colloidal substances occur- 
ring in the animal organism, consist of much smaller 
particles than artificially prepared colloids. Thus 
haemoglobin will pass through much less permeable 
membranes than colloidal metals, and serum, albumen, 
and - protalbumoses are correspondingly finer in the 
order given. This may partially account for their 
ability to pass through certain membranes. Donnan 
has shown that the permeability of a membrane to a 
simple ion is greatly affected by the presence of a colloid. 
In some cases the colloid is hydrolised by some un- 
known means in the presence of an inert membrane 
and an electric potential is created. In both these 
cases the difference between a living and a dead 
organism must not be overlooked, though its import- 
ance should not be exaggerated. 

The nature of materials used for food is so varied 
and the products of their digestion are so numerous 
that for anyone who realises their essentially colloidal 
nature, it is easy to see that any change of state may 
produce a profound disturbance in the whole system, 
and that such a disturbance may appear to be quite 


out of proportion to the chemical activity of any 
compound or element which may be present. For this 
reason there can be no general cure for all forms of 
indigestion, as each has its specific cause. If any such 
general remedy could exist it would be a substance 
which would effect the conversion of any food sub- 
stance into a colloidal sol of a nutritive and non-toxic 

Similarly, it is possible to see that improper food, 
unsuitably prepared, the absence of sufficient air, and 
the neglect of sanitary and hygienic precautions may 
effect changes which are quite disproportionate to the 
actual weight of " dirt " or other objectionable matter 
present. The normal state of the body fluids is easily 
disturbed, and whilst it is almost as easily restored 
under healthy conditions of life, restoration is made 
difficult or even impossible if the conditions are un- 



COLLOIDS have long been used more or less unwittingly 
in medicine, the colloidal state being the only one in 
which certain medicaments can be administered, whilst 
others exhibited as tinctures are converted into 
colloids on dilution. Such crude forms are necessarily 
subject to many disadvantages, and the true signifi- 
cance of their colloidal nature not having been recog- 
nised it is only natural that they should not be either 
as certain in action nor as free from objectionable 
properties as colloids which have been specially pre- 
pared so as to secure the maximum colloidal efficiency. 
Thus, tincture of podophyllin and other resinous sub- 
stances are precipitated on diluting them sufficiently 
with water, with the consequent formation of a small 
proportion of colloidal sol. This sol is the most active 
therapeutic constituent, and the remaining material 
is only useful medicinally when it has been converted 
by the action of the body fluids into an assimilable 
form. This conversion is accompanied by a serious 
loss of material, both directly, by its conversion into 
inert or undesirable substances, and indirectly by its 
transport to portions of the organism where it cannot 
exercise the desired effect. Consequently, the acci- 
dental production of therapeutic agents in colloidal 



form results in uncertainty of action, the production 
of undesirable side reactions, and necessitates the 
administration of large doses, the greater part of which 
is inert, or, in some cases, somewhat harmful to the 
patient. These disadvantages were unavoidable so 
long as no satisfactory colloidal preparations were 
available, but with the increase in the number and 
efficiency of the latter, the science of pharmacology 
and the practice of medicine will, it is anticipated, 
make rapid progress. 

The most widely-used preparations of a highly 
colloidal character are the embrocations and liniments 
used externally or those administered internally in the 
form of emulsions of cod liver oil, petroleum, etc. 
These have proved a convenient and satisfactory means 
of introducing certain liquids in varying degrees of 
dilution, under conditions in which ordinary solvents 
are inadmissible. 

Such emulsions are truly colloidal in character, the 
active liquid being usually present as the disperse 
phase, whilst the continuous phase is of a different 
character, such as water to which a small proportion 
of an emulsifying agent usually albumen or a soap 
is added. Other active therapeutic agents may usually 
be present in solution in the aqueous phase, it being 
an additional advantage possessed by emulsions that 
they permit the simultaneous exhibition of two or more 
active agents in any desired degree of concentration. 

Emulsions of the kind just mentioned must not be 
confused with the colloidal sols described later. Even 
the most elegant emulsions are very coarse compared 
with the sols, and the penetrating power and general 


activity of the latter are correspondingly greater than 
that of emulsions. 

The customary administration of any remedy 
quite apart from the particular substance or drug 
which it may contain is primarily based on the 
assumption that such a remedy has a specific reaction 
either with a substance in the body (such as the action 
of pepsine on the undigested food) or an equally definite, 
but less understood, reaction whereby certain organs 
are stimulated to unusual effort, as in the administra- 
tion of emetics or purgatives. It is generally supposed 
that the effect is roughly proportional to the dose 
administered, though it is recognised that the optimum 
dose differs with different patients. In some cases 
particularly in the administration of mercury com- 
pounds it is also realised that minute quantities 
administered frequently have an effect which is 
entirely different from that of the same substance 
administered in a single and large dose. Still more 
striking is the fact previously mentioned, that with 
some remedies the changes are out of all proportion 
to the dose which may be administered. The great 
changes which occur in certain diseases are prevented, 
and the normal state is restored by quantities of 
chemical agents which appear ridiculously small when 
regarded as definite reagents. But such a condition 
is a well-known characteristic of colloidal fluids, in 
which even a few drops of solution will effect a solidifica- 
tion of a large volume of material. The coagulation of 
milk by rennet or acid, and that of blood after a short 
exposure to air, are typical illustrations of such a 
change. The extraordinarily rapid action of minute 


doses of some poisons is probably a similar effect. 
Bearing in mind these great changes in condition 
which result from the action of small amounts of active 
agents, it is easy to see that a slight excess or deficiency 
of some element present in minute proportions in the 
organism may effect a profound change in the action 
of that organism. The deficiency of phosphorus in 
certain nervous diseases is well recognised, and various 
methods of supplying it have met with encouraging 
results. There is, however, a curious idea extant, that 
an element in which there is a deficiency should be 
administered in the same form as that in which it 
exists in the body. For instance, there is a popular 
idea that glycophosphates are superior to any other 
phosphorus compounds, because the phosphorus in 
the brain is chiefly found as a glycophosphate. This 
is quite a mistake, as will readily be seen if other 
analogous cases are considered. For instance, sugar 
is stored in the liver in the form of glycogen, but to 
administer glycogen orally would be useless, as it is 
destroyed in the stomach. It is essential that any 
medicine should be administered in such a form that 
its essential constituent will travel through the body 
until it reaches the part where it is required, and that 
it shall arrive at that organ in such a state as to be 
used to the greatest advantage. To administer lecithin 
because lecithin has been isolated from the brain 
substance is to misunderstand the chemical changes 
which take place in assimilation, and to supply the 
subject with a material in a form from which it has to 
be converted to something more suitable. The fact 
that this conversion occurs merely shows how marvel- 


lous an alchemist is the human organism ; it is no 
reason for the administration of chemical agents in 
unsuitable forms. 

The principle underlying the treatment of disease 
by the administration of chemical compounds is much 
more easily understood when it is realised that the 
reactions deal largely with colloidal materials, and 
that they may be effected most efficiently and with a 
minimum of disturbance to other organs by basing 
the treatment on this principle. 

This fact has been recognised in a half-hearted way 
for some years, but its implications were scarcely 
realised until a few years ago. This was due to a 
number of causes, of which the two most important 
were the difficulty of studying the special properties of 
substances in the colloidal state with the appliances 
then at hand, and the difficulty experienced in obtain- 
ing active colloidal fluids which were isotonic with 
and therefore stable in the body fluids to which they 
were applied. The work of Ehrlich and others may, 
in certain respects, be regarded as attempting to 
supply elements of a highly toxic character, such as 
arsenic, in such a form that they would affect the 
disease-creating germs without harming the patient 
or host. Such methods suffer from obvious draw- 
backs, such as the caustic, irritant, or even toxic effect 
of the stabilising organic compound, and as the com- 
plexity of the compounds was increased, their essentially 
colloidal character gradually receded into the back- 
ground of the minds of the investigators until it was 
wholly overlooked. 

Colloidal fluids only retain their characteristic 


properties so long as their active ingredient is in a 
properly dispersed and suitable colloidal state. In the 
presence of very small quantities of certain salts, the 
ions or ultimate particles of which have an electric 
charge which is opposite in sign to that of the active 
colloid, the latter will be coagulated and rendered in- 
active, unless they have been protected by some other 
colloid. In the latter case, coagulation or precipitation 
can only occur when the protective agent has been 
destroyed or removed. 

Medical possibilities of colloids. From what has 
already been stated it will be seen that the application 
of colloidal sols to diseased conditions of the human 
body is distinctly encouraging, but like all other new 
ideas it has had its share of drawbacks and discourage- 
ments, due in almost every instance to ignorance. 
Among other causes the premature supply of improperly 
prepared and unstable colloids has been one of the 
most serious sources of trouble. 

Shortly after the definite recognition of the colloidal 
nature of the chief body fluids was effected, the 
enormous possibilities which might result from the 
application of colloidal disinfectants and medicines 
were rapidly recognised by German investigators ; a 
number of colloidal substances was placed on the 
market and their therapeutic properties were carefully 
and vigorously " boomed " in this country and 

It was soon found, however, that most of these 
preparations rapidly deteriorated in value ; some of 
them were so unstable that they contained no active 
colloid at the time when they were used, and others 


not being isotonic with the physiological fluids in the 
diseased organs to which they were applied were 
coagulated immediately after their administration to 
the patient. 

Many attempts to secure stability by means of 
organic compounds were made, and eventually the 
main difficulties were overcome especially with regard 
to certain colloidal elements. One of the chief causes 
of trouble was due to the fact that if a colloidal sub- 
stance is prepared in the purest possible state in a 
disperse medium (such as water) of great purity, the 
product will be highly unstable. Even a trace of 
material of the opposite electric sign will cause the 
precipitation of the colloid. If, on the contrary, the 
substance is converted into the colloidal state in the 
presence of certain other colloids and of certain salts, 
the desired colloid will not have its activity impaired 
in the least degree, but it will be quite stable and can be 
mixed with normal blood or other body fluids without 
being rendered inactive by them. The salts and 
additional colloids exercise a protective action on the 
colloid chiefly under consideration, and so enable it to 
be used under circumstances which would otherwise 
be impossible. The therapeutic action of the protec- 
tive agent must not be overlooked ; usually it appears 
to be negligible, but occasionally it has been observed 
to be of considerable importance. 

Failure to realise the necessity for stabilising the 
remedial colloids by rendering them isotonic with the 
blood serum, and protecting them against precipitation 
by undesirable agents, was thus one of the chief causes 
of failure of the earlier investigators, but it has been 


entirely overcome in the case of a large number of 
colloidal sols mentioned later, and these are quite 
stable and effective. Yet in consequence of the failure 
which resulted from such ignorance of the essential 
properties of all colloidal fluids, British medical men 
were at first rightly averse to using colloidal pre- 
parations, and the subject remained in a parlous 
state for some time. In fact, it so remained until 
suitable methods of preparing stable and isotonic 
colloidal sols were discovered in 1910-1913 by the 
late Henry Crookes a son of Sir Wm. Crookes and 
were extended and improved by his colleagues and 
successors, as well as by other investigators. 



ANY substance can be obtained in the colloidal state 
if the conditions under which it is prepared are suit- 
able. All colloidal sols are prepared by either 

(1) Dispersing or breaking down the larger particles 
in the presence of a suitable fluid ; or 

(2) By " condensing " particles in solution until 
they form larger suspensoid particles. 

The dispersion may be effected 

(a) Mechanically, as by grinding the substance 
and fluid together ; l 

(b) By dilution, as when a gum is dissolved in 
alcohol solution and the solution poured into a large 
volume of water ; 

(c) By using electrodes of the substance to be dis- 
persed immersed in a suitable liquid and passing an 
electric current through them ; 

(d) By the addition of a suitable electrolyte (such 

1 Colloidal solutions must not be confounded with the sugges- 
tions made by homcepathists with respect to prolonged trituration 
of a solid material or to the administration of small doses at regular 

No trituration, however prolonged, will convert some materials 
into a colloidal sol state, and even those which can be converted 
are too much contaminated with non-colloidal material and are 
too unstable to be of much service. As regards dosage, it is a 
well-known characteristic of all colloidal reactions that if the whole 
of the reagent is added rapidly its effect is much greater than if it 
is added in small quantities at a time. 



as an acid or alkali) to a colloidal gel. From the 
analogy between this process and that of animal 
digestion it is frequently termed peptisation. 

The condensation may be effected by chemical 
reduction, oxidation, hydrolysis, or double decom- 
position. Thus, colloidal gold sol is readily obtained 
by reducing a dilute solution of gold chloride, formic 
aldehyde, or phosphorus in the presence of potassium 
carbonate. Colloidal sulphur sol may be obtained by 
adding a solution of sodium hyposulphite drop by 
drop to a dilute solution of sulphuric acid, heating 
the mixture to 80 C. for a short time, filtering off 
any insoluble sulphur and neutralising with sodium 

Although many colloidal sols are made by hydrolysis 
(i.e. by the action of water on them) this is seldom 
used as a method of preparation. The methods of 
preparation just indicated do not as a rule yield 
colloids which are stable in the presence of serum. 
For this purpose they must be modified so as to pro- 
duce a stable fluid. It is most important to observe 
that it is relatively easy to produce a colloidal sol of 
low stability and containing a considerable proportion 
of impurities ; it is peculiarly difficult to prepare pure 
sols which remain stable when mixed with the blood- 
serum and other physiological fluids. Yet the use of 
impure and unstable sols is so serious that no pains 
must be spared in ensuring the purity and stability 
of the sols used for remedial purposes, and particu- 
larly those which are administered by intravenous 
or intramuscular injection. For these reasons, the 
remedial colloidal sols prepared by the amateur should 


not be used until exhaustive tests have proved their 
efficacy and stability. The author is aware of a number 
of severe cases of poisoning which were due solely to 
the use of impure colloids with a very low degree of 
stability. As many colloidal sols of high stability and 
suitability for administration either orally or hypo- 
dermically can now be purchased, there is little or no 
advantage to be gained by medical men preparing 
these sols. 

The stabilising or protecting of a colloidal sol depends 
on its being in a state of equilibrium between the 
forces tending to cause these small particles to 
coalesce (surface tension) and those tending to cause 
dispersion of the colloid throughout the medium. 
Stability appears to be due, in most cases, to a union 
of the particles to be stabilised with those of the pro- 
tective colloid or with ions which have a stabilising 
action. Zsigmondy maintains that stability is wholly 
due to the equilibrium between the adsorption and 
dissociation of ions by colloidal particles. The in- 
stability which is most serious in colloidal sols used as 
medicines is that which results in coagulation. 

Stability is secured in a variety of ways, including 
the following : 

(a) Preparing the sol in the presence of those sub- 
stances in which it is required to be stable, i.e. by 
substituting an appropriate fluid for water as a solvent 
for the various substances from which the colloid is 
produced. Thus colloidal sulphur, prepared in a 
solution in which water is replaced by a physiological 
salt solution, is much more stable after injection into 
the blood than colloidal sulphur prepared in pure 


water. On the other hand, the former is liable to set 
up undesirable reactions within the body unless 
special precautions are taken to remove the undesir- 
able salts by a process of selective dialysis. 

(b) Adding a protective agent such as gelatin or pro- 
talbinic acid prior to producing the sol. 

(c) Preparing the sol so that all the dispersed par- 
ticles are of the same size and without any appreciable 
surface tension in the dispersing fluid. 

(d) The presence of chlorine or of other charac- 
teristic ions appears to be essential to the stability 
of positive sols. If these ions are removed the sols are 

(e) Removing the greater part (but not the last traces) 
of electrolytes. This method is inapplicable to colloids 
used for medical purposes. 

Assaying sols. It is of utmost importance to de- 
termine the activity of a sol just prior to its use unless 
it is definitely known that it is sufficiently stable for 
its activity to be relied on implicitly. 

The percentage of active colloid cannot be de- 
termined by any of the ordinary chemical methods as 
the colloidal state is physical rather than chemical in 
character. Thus, a colloidal solution of silver gives no 
precipitate with a solution of a chloride, a colloidal 
solution of iodine does not produce a blue colour with 
starch solution. Hence, it sometimes happens that a 
chemist may report that a certain solution does not 
contain a particular element or compound if the latter 
is in a colloidal sol state. By appropriate treatment 
usually by converting the substance into the crystalloid 
state the ordinary methods may be applied, but they 


do not differentiate between the proportions of colloidal 
and crystalloidal substance when both are present. 

The chief methods of determining the activity and 
therefore the value of the sol are : 

(a) Observation of the movement of the particles 
by means of an ultra-microscope. 

(b) Observation of the intensity of the Tyndall 

(c) Determination of the gold number. 

(d) Observation of the time taken for a deposit 
to form. 

(e) Observation of the effect of the addition of 
the solution to serum or other characteristic physio- 
logical fluid. 

A. Arc Lamp. B. Slit. C. Primary Lens. D. Secondary 'Lens. 
E. Condenser ( I in. objective). F. Cuvette. G. Microscope. 


(a) The ultra-microsoope affords the simplest and 
most rapid means of ascertaining the activity of the 
colloidal particles in a sol. When properly prepared, 
colloidal sols are transparent or slightly opalescent, 
coloured or colourless, pass readily through a filter 
paper, are apparently homogeneous in chemical be- 
haviour but under the ultra-microscope are seen to 
contain minute particles in a state of rapid motion, the 
particles being comparable in size to those of molecules 


in crystalloid solutions. In some colloidal sols the 
particles are too small for their movements to be 
observed in the ultra-microscope (i.e. they are less 
than about 30 /UL/UL in diameter) . The ultra-microscope 
is based on the fact that the existence of particles 
which are quite invisible to direct vision may be readily 
recognised by passing a beam of light across the space in 
which they occur. The beam of light from a lantern 
is in itself invisible, but the particles of dust present 
in the air which are also invisible reflect the light 
in various directions, so that we recognise the presence 
of these particles by their action on the light. 

Zsigmondy applies the same principle to colloidal 
particles by passing a very concentrated and powerful 
beam of light horizontally through the liquid to be 
examined and then views the liquid against a black 
background through an ordinary microscope. If the 
liquid consists of a solution of a crystalline salt the 
field of the microscope remains dark, but if an active 
colloidal substance is substituted the field is at once 
occupied by minute specks of light which dart hither 
and thither in a wholly irregular manner. The ultra- 
microscope consists of a powerful source of light an 
arc lamp or the sun which sends a beam of light 
through a suitable slit 0-002 to 0-02 in. wide and 0-004 
to 0-08 in. high, the light being focussed by a telescopic 
objective of about 0-4 in. focus. A second similar lens 
of about 3 in. focus forms an image of the slit in the 
plane of a condenser, the latter consisting of a micro- 
scope objective, whereby a reduced image of the slit 
is thrown into the solution to be examined. A polariser 
may be inserted between the slit and the second lens 


if polarised light is desired, and all extraneous light 
may be cut off by suitably disposed diaphragms. The 
solution to be assayed is contained in a specially shaped 
glass vessel termed a cuvette, which consists of an 
accurately shaped rectangular cell with a small tube 
at each end to form an outlet and inlet respectively. 
By passing a current of specially distilled water 
through the cuvette it is readily cleaned and the col- 
loidal solution can be admitted, discharged, and the 
cell washed as required. 


The light passing horizontally through the solution 
is reflected by suspensoid particles, and if an ordi- 
nary microscope is used to examine the solution in the 
cuvette the field will be illuminated by brilliant specks 
of light if a colloidal sol is being examined, but will be 
dark if a crystalloid solution is used. If the cuvette is 
filled with an active colloidal sol, the movements of 
the particles are readily observable, and then if to 
this active liquid is added another containing either 
a colloid of opposite electrical sign or some other sub- 


stance on which the active colloid can exert itself, the 
field rapidly darkens because the active colloid and 
the reagent combine and settle to the lower part of 
the cell and so out of the beam of light. 

An active colloid which has, for any reason, become 
unstable will show very few specks of light in the ultra- 
microscope, and their movement will be slow and 
wholly different from a freshly prepared colloid. By 
this simple means, the activity of a colloidal fluid may 
be ascertained in a few minutes and all uncertainties 
in this respect at once removed. Without such an 
instrument, useless, inactive, and unstable colloidal 
preparations might be administered instead of active 
ones. The use of an ultra-microscope was particularly 
necessary when the uncertain colloids prepared by 
electrical methods or by reduction from unsuitable 
solutions were used, but at that time, unfortunately, 
such instruments were not available in this country. 
During the past five years, perfectly stable colloidal 
preparations have been available in this country, and 
as they can be relied upon, if prepared by a good firm, 
the general use of the ultra-microscope is no longer 

Incidentally, it may be mentioned that the ultra- 
microscope has been invaluable in recognising the dis- 
similarity between normal and infected serum and the 
effect of prepared colloids upon the characteristic 
colloidal eccentricity of such substances as syphilitic 
serum. Normal serum is a saline colloidal solution of 
insoluble protein protected by soluble protein (aliphatic 
amino-acids). In syphilis, the proportion of colloidal 
matter in the serum is supernormal, and especially in 


the cerebro-spinal fluid, and the charge carried by the 
protein is positive. 

(b) The Tyndall phenomenon first investigated by 
John Tyndall, 1 who found that light passed through a 
gas or liquid containing particles in suspension even 
when these are so small as to be ultra-microscopic 
produce a delicate blue colour the intensity of which 
is roughly proportional to the number of particles. 
Larger particles produce a white tint as they are not 
small enough to scatter only the shortest waves of light. 

If a concentrated beam of light from an arc lamp is 
passed through a slit placed in its focus, next through 
the solution in a rectangular vessel and then observed 
with a mounted Nicol prism, it will be found that the 
polarisation of the light is affected by the colloidal 
particles. If these are less than 100 p.^ in diameter 
the polarisation is complete, and the Nicol must be 
turned through 90 to depolarise it. For larger ones, a 
lesser angle will suffice. If a selenite plate is substi- 
tuted for the Nicol prism, the light which has been 
polarised almost completely by the solution will pro- 
duce vivid colour effects. These coloured rings form 
an extremely delicate means of estimating the number 
of particles in suspension in the solution, the diameter 
of the beam of light required to produce the rings being 
inversely proportional to the number of colloidal 
particles in the solution. Thus, a large beam of light is 
needed for distilled. water, whilst with a good colloidal 
solution so small a beam as to be scarcely visible will 
produce vivid colours with selenite. 

1 Proc. Roy. Soc. Lond., 1868, 17, 223 ; Phil. Mag., 1869, (4), 37, 


A true solution devoid of all colloidal particles does 
not show the Tyndall effect, though it is extremely 
difficult to obtain any liquid which does not give at 
least a faint indication. Fluorescent solutions (such 




, 4 

'K I 

1 i 
1 1 

1 H=| 


jT] i< 



lJ A\ 

i! i 


FIG. 4. TYNDALLMETER (Vertical Section and Plan). 

as quinine disulphate, dilute eosin solution, etc.) which 
might otherwise be mistaken for colloidal sols, do not 
show this effect. 

A convenient arrangement for applying the Tyndall 
beam to colloidal liquids is that devised by Tolman 
and Vliet. It consists of an electric light bulb B, a 


condensing lens L, giving a beam of parallel light which 
passes through the diaphragm D, and a Macbeth illu- 
minator for measuring the intensity of the Tyndall 
beam T. A cylindrical tube is introduced at T through 
which the liquid to be examined is admitted and dis- 
charged. The tubes A x and A 2 are provided to absorb 
the beam after it has passed through the colloidal 
liquid, and also to serve as a dark ground on which to 
view the Tyndall beam. The central chamber in which 
the colloid to be examined is placed is about i in. 
diameter and 4 in. long, and the tubes A x and A 2 are 
about the same diameter and 12 in. long. The illumi- 
nator is an electric lamp of about 3O-candle power at 6 
to 8 volts, capable of adjustment so that the apparatus 
may be standardised, the light being usually ad- 
justed so as to give a brightness of 22-5 foot candles, 
though any convenient figure may be used. The in- 
tensity of the Tyndall beam is fairly proportional to 
the concentration of the colloid when the dispersion 
is great, but when the concentration is much higher 
than 0-5 gm. per litre the intensity is not proportional 
as the increased turpidity of the sol prevents the light 
passing through the liquid. It should be noted that 
the size of the particles must be taken into account, as 
in the following formulae : 

T=knd* for small particles 
Tk l nd 6 for large particles 

where T is the intensity of the beam, k and k l are 
constants ; n is the number of particles per cb. cm., 
and d is the diameter of the particles. 

(c) The Gold number is a measure of the protective 


power of a colloid against the tendency of other colloids, 
etc., to effect precipitation ; it is also a measure of the 
stability of the colloidal sol. The gold number is 
defined by Zsigmondy 1 as the weight in mgms. of 
colloid which just fails to prevent the change from 
red to violet in 10 cc. of gold solution (containing 
0-0053 to 0-0058 per cent of gold) when i cc. of 10 
per cent solution of sodium chloride is added to the 
sol. Hence, the lower the gold number the greater the 
protective effect of the colloid or the greater the 
stability of the sol examined. 

The gold number is found as follows : Three portions, 
a, b, and c, containing 0*01, o-i and I cc. of a suitable 
protecting colloid such as gelatin and i cc. of the colloid 
to be tested, are placed in three small beakers and well 
mixed with 10 cc. of gold collosol. After three minutes 
i cc. of 10 per cent solution of sodium chloride is added 
to each and mixed. Assuming there is a colour change 
in a but not in b the gold number lies between o-oi and 
o-i. For a more accurate determination, repeat with a 
fresh series, using 0-02, 0-05, and 0-07 cc. of colloid. 
The following gold numbers are useful : 

Class of protective 

Gelatin and glues . . . 0-005-0-010 

Isinglass 0-010-0-020 


Casein o-oio 

Good gum arabic . . . 0-150-0-250 II 

Dextrin 6-000-20-000 1 -QJ 

Potato starch . (about) 25-000 

Silicic acid oo IV 

The stability number is a useful modification of the 
test, as applied to the determination of the stability 

1 Zeits. anal. Chem., 1902, 40, 697. 


of a colloidal sol. It is found by first selecting a sub- 
stance which will decompose the colloidal sol, preparing 
a suitable solution of this substance, and then adding 
it to a known volume of the sol to be examined. The 
amount of substance required to just destroy the 
activity of I c.c. of the colloidal sol, as observable 
under the ultra-microscope, is the stability number. 

(d) The time required before a colloidal sol will form 
a deposit is a crude, but useful, measure of its stability. 
With sols of poor quality the time is very short, but 
properly stabilised sols are remarkably durable. The 
author kept a sample of colloidal iodine dispersed in 
33 times its weight of mineral oil for three years and 
found that it was as active and free from deposit as 
when first prepared. Great care is needed when making 
comparisons of colloids on a time basis, as so many 
variable factors may occur. The influence of heat 
and light must not be overlooked, whilst even more 
important may be the effect of traces of material dis- 
solved out of the glass of which the vessel containing 
the colloid is composed. Traces of dust or organic 
matter in the vessel used may have a serious effect, 
and for this reason colloidal sols should not be stored 
in corked bottles. If proper care is taken to stabilise 
the sols, those used remedially can be stored indefi- 
nitely in ordinary glass-stoppered bottles as the 
stabilising agents which prevent the decomposition 
of the sols by silicates or alkalies dissolved from the 
glass do not affect the physiological activity of the 

(e) The effect of serum or other physiological fluids 
on a sol intended for medical or surgical purposes 


should be fully investigated before employing the sol. 
Unless this is done, sols may be used which are quite 
useless owing to their premature decomposition. This 
applies particularly to " home-made " preparations ; 
those bought from reliable manufacturers have usually 
been investigated by independent authorities and their 
suitability can be ascertained by enquiry. Speaking 
broadly, pure suspensions of a colloid in water are 
quite useless physiologically and pathologically, as 
they are decomposed immediately they enter the blood 
stream. By preparing them in a suitable manner with 
the proper stabilising agent in each case, this objection 
may be completely overcome. 



IT has long been the desire of physicians and sanitarians 
to find a series of substances which will destroy disease- 
producing germs and yet prove harmless to human 
beings or even to domestic birds and animals. Many 
attempts have been made to obtain compounds 
analogous to carbolic acid, with a high germicidal and 
low toxic power, but only a meagre degree of success 
has been reached. This is only to be expected when 
it is realised that the human organism is composed of 
an indefinite number of cells and that any substance 
which kills bacteria or other disease-producing 
organisms is almost certain to have a similar action 
on these cells. The difference in action is merely one 
of degree, and is therefore subject to limitations and 
accompanied by risks which are far from satisfactory. 

Moreover, some of the most virulent germs are able 
to flourish in solutions of carbolic acid (phenol) and 
other well-known disinfectants of a strength which 
would be poisonous to human beings, and also the 
evolution of germs of one kind into those of another 
renders almost chimerical the search for a general germ- 
poison which is non-toxic to human beings. 

Fortunately, the recognition of bacteria and their 
products as essentially colloidal in character has greatly 
facilitated the study of disinfection. It is now realised 



that disregarding the fact that bacteria are alive 
they may owing to their colloidal character and that 
of the toxins and some other substances they pro- 
duce be destroyed by substances which bear an 
electrical charge opposite to that of the bacteria or 
their colloidal products. The effect of an ordinary 
disinfectant on bacteria is the result of its adsorption 
by the latter, forming either a chemical compound, as 
appears to be the case with formalin, or a distribution 
of various phases in accordance with the well-known 
law of adsorption of colloids. In the latter case, 
colloids of opposite electric charge will precipitate 
each other so long as neither is in great excess, but if 
either colloid is in excess both will be rendered inactive 
though no precipitation may occur. 

The great advantage of dealing with germs as colloids 
lies in the fact that the agents used for their coagula- 
tion and consequent destruction are not necessarily 
poisonous an advantage which becomes of utmost im- 
portance when it is desired to destroy the bacteria in 
corpore villi. In other cases, where the use of phenol 
and other poisonous substances is less objectionable, 
their lower cost may rightly be taken into considera- 
tion. Some of the most fruitful results in this line of 
research are those which have followed the discovery 
by the late Henry Crookes in 1910 that certain metals 
when in a colloidal state have a highly germicidal 
action, but are quite harmless to human beings. It 
was previously known that certain finely divided 
metals had a feeble toxic action on the lower forms of 
plant life, and that the germicidal power of certain 
metallic salts depends to a very large extent on the 


degree of ionisation and on the specific properties of 
the individual ions, those of the metal having the 
chief germicidal power. In other words, the greater 
the extent to which the metal is set free in a very 
dilute solution of its salts, the greater is the germicidal 
power of the solution ! By converting the metal into 
the colloidal state it may be applied in a much more 
concentrated form and with correspondingly better 

The importance of this twofold fact has been largely 
obscured, partly by the germicidal properties of some 
substances apart from their degree of ionic dissociation, 
partly by the manner in which some substances 
are adsorbed by the products accompanying the 
bacteria, and so are rendered inert before the latter 
are affected, and partly because of the ignorance of 
the means of preparing colloidal metals in a form 
sufficiently stable for administration as medicines. 

Equally unfortunate was the death of Mr. Crookes 
before he had been able to extend the results of his 
discovery, though these difficulties and drawbacks 
have now been overcome and are chiefly of historical 
interest. It is now definitely known that the germi- 
cidal properties of certain colloidal metals are based 
partly on the chemical action of the metals themselves, 
different metals having greater specific action on some 
bacteria than on others, but chiefly on the fact that 
metals are in the colloidal (sol) state. 

These colloidal metals of which gold and silver 
are the best known consist of such minute particles 
that the latter have ample space for an extremely 
active movement without touching one another. 


Moreover, by virtue of a property well known in 
physics the particles having a like electric charge 
tend to repel one another and thus increase the 
stability of the liquid. When such metallic particles 
are added to a fluid containing in solution, suspension, 
or in that intermediate state we recognise as colloidal, 
particles bearing the opposite electrical charge or in 
some cases if the particles are neutral coagulation 
or precipitation rapidly occurs. 

The germicidal action of colloidal metals, such as 
silver and mercury, at a concentration of i : 20,000 
is clearly shown by the following test made by the 
late Henry Crookes : 

Silver and mercury " Collosols " of the normal 
strength (i in 2000) were diluted with 9 times their 
quantity of nutrient broth (i in 20,000), and 10 cc. of 
this mixture were infected with two loopfuls of a 
vigorous culture of B. coli communis ; after shaking, 
so as to mix thoroughly, streak cultures were made 
quickly on agar plates, the first within ten seconds, 
then at two, four, six, eight, and ten minute intervals. 
These plates were incubated at 37 C. for forty-eight 
hours, and gave the following results : 

Silver " Collosol " (i in 20,000) Mercury " Collosol " (i in 20,000) 

with B. coli communis with B. coli communis 

After 10 seconds Growth After 10 seconds Growth 
2 minutes ,,2 minutes No growth 

4 4 

>, 6 ,, No growth ,, 6 

o ,, ,, ,, o ,, ,, 

10 10 

In each case the blank or control streak gave a vigorous 


These experiments were repeated with silver and 
mercury " Collosols " at the normal strength of one 
part in two thousand. In every case, B. coli communis 
was killed within ten seconds, the only growths on the 
agar plates being those of the untreated control 
streaks. Several comparative tests were made with 
the gonococcus grown on agar plates smeared with 
fresh blood, with the usual precautions. A plate 
showing a vigorous growth and answering to the 
typical tests (viz. Gram-negative, no growth on 
gelatin or agar at 20 C. without fresh blood, but 
vigorous growth at 37 C. on agar with fresh blood, 
and displaying the well-known diplococcus in pus cells) 
was swabbed with " Collosol " silver for two minutes, 
after which time streak cultures were taken and 
transplanted to agar plates smeared with fresh blood 
as before, at intervals of two, four, six, eight, and ten 
minutes, and incubated in the usual way at 37 C. 
Result. No growth whatever. 

Many series of experiments similar to this gave 
similar results ; for instance, a young vigorous growth 
of B. tuber colosis was killed by " Collosol " silver 
(l in 2000) in four minutes. Staphylococcus pyogenes, 
various Streptococci, and other pathogenic organisms, 
are all killed in three or four minutes ; in fact, no 
microbe is known that is not killed by this colloid in 
laboratory experiments in six minutes. 

The following experiments were made by W. J. 
Simpson, C.M.G., M.D., etc., Professor of Hygiene, 
King's College, London, and R. Tanner Hewlett, M.D. 
(Lond.), F.R.C.P. (Lond.), Professor of Bacteriology in 
the University of London, were printed in the 


Lancet of 12 December, 1914, and are of special 

Drs. Simpson and Hewlett mixed Silver Collosol 
solution with nutrient broth in various dilutions, 
taking 10 cc. of each in a tube. These were inoculated 
with one drop of 24-hour broth culture of the typhoid 
bacillus, incubated, and subcultures made after vary- 
ing times. For the sake of comparison, similar experi- 
ments were carried out with corrosive sublimate 
under the same conditions. The results were as shown 
in the tables : 


500 per million 

zoo ,, 





15 min. 

Subcultures made after 

30 min. i hour 2 hours 

O O 

tubes after 
24 hours 3 days 

WITH CORROSIVE Subcultures made after 
SUBLIMATE 15 min. 30 min. i hour 2 hrs. 24 hrs. 

tubes after 
3 days 

500 per million . + 


100 ,, ,, + 



50 . + 

+ 000 

25 . + 

+ o o o 

10 ,, + 

+ + + + 

5 + 

+ + + o 

+ = growth ; o =no growth in the subcultures. 

A comparison revealing such a small difference in 
germicidal power between the collosol and corrosive 
sublimate, considered in the light of the absolute 
non-toxicity of the collosol, is surely remarkable and 
cannot fail to evoke considerable interest. 

Many other experiments of a similar nature have 


been made by chemists and medical men, all testifying 
to the value of " Collosols " as bactericides. 

On the 2Oth May, 1913, two plates of nutrient 
gelatin were exposed on the window-sill for half an 
hour. A had been covered previously with " Collosol 
Argentum " for five minutes ; B was untreated. Both 
plates were incubated for forty-eight hours at 20 C. ; 
after which, A remained sterile whilst B contained 
about 350 colonies of microbes. Figs. 5 and 6 illustrate 
this preservative effect of " Collosol Argentum." 

It might be suggested that a liquid containing only 
one part of colloidal metal in 2,000 of fluid would be 
too weak to be of use, but this is not the case. There 
are at least 20,000 million active particles of metal in 
i cc. (=15 drops) of properly prepared colloidal silver of 
this concentration, and one great advantage of colloidal 
elements in such a low concentration is their complete 
harmlessness to the patient. 

Not all elements in the colloidal state have a germi- 
cidal action. The following table, based on Henry 
Crookes' investigations, is interesting in this connec- 
tion : 

No germicidal action : Gold, platinum, palladium, 
rhodium, indium, tantalum, cadium, magnesium, tin, 
graphite, selenium, sulphur (sulphur has a strong, 
stimulating action). 

Slight germicidal action : Bismuth, lead, aluminium, 
zinc, copper. 

Strong germicidal action: Thorium, cobalt, silver, 
mercury, antimony, mercuric cyanide, mercuric 
chloride, arsenious acid. 

The germicidal action of metals and some other 


substances is clearly shown in Figs. 5 to 18, which are 
reproduced from photographs taken by Hy. Crookes 
of Petri dishes containing fish-agar, or other nutrient 
medium inoculated with various bacteria and kept 
under conditions favourable for their incubation and 
development. In the centre of each dish was placed a 
piece of the substance whose action was to be examined 
and its effect is clearly shown. 

On examining the illustrations showing a dish con- 
taining a germicidal metal it will be seen that sur- 
rounding the latter is a vacant space in which no 
bacteria have grown, around it is a dense ring in which 
the germs have flourished to an abnormal degree, and 
between this ring and the circumference of the dish is 
practically the same as though no germicide were 
present. The cause of this arrangement which is 
particularly marked in the case of silver (Fig. 10) is 
the germicidal action of the minute amount of colloidal 
silver which has been formed immediately around the 
metal, whilst further away a still smaller proportion 
of the colloidal silver has a stimulating action on the 
bacteria. Still further away there is no colloidal silver, 
and the bacteria grow in the normal manner. The 
growth of the same bacteria in the presence of a 
germicidal and inert colloidal metal may be compared 
by observing the differences between Figs. 5, 6 and 
10 ; the former, which shows the action of colloidal 
silver, exhibits the characteristic features very clearly ; 
in the latter, which shows the result of using non- 
germicidal colloidal gold, these features are absent and 
the bacterial growth is fairly uniform. 

The amount of colloidal metal produced under the 


N O 






^ U 

c . 
.2 ffi 

fr - 


foregoing experiments is almost infinitesimal, so that 
its germicidal effect is very striking. Much more 
impressive results are obtained by the addition of a 
properly prepared colloidal solution to an inoculated 
medium the bacteria then being destroyed quite 
rapidly but the reproduced photographs show in an 
unmistakably clear manner the great potentialities 
of colloidal metals even under conditions which are 
not particularly favourable to their use. It has been 
estimated that in the death zone, where the concentra- 
tion of the colloidal metal is greatest, the latter does not 
exceed twenty-five parts per million parts of nutrient 

The germicidal action of certain metals in the 
colloidal state having been demonstrated, it only 
remained to apply them to the human subject, and 
this has been done in a large number of cases with 
astonishingly successful results. It is not suggested 
that colloidal metal sols should replace the customary 
disinfectants for sterilising excreta, vessels of various 
kinds and for other general purposes, but for internal 
administration, either orally or hypodermically, they 
have the advantage of being rapidly fatal to the para- 
sites both bacterial and otherwise without any toxic 
action on the host. 



TURNING now to the use of colloidal liquids in the 
relief or cure of disease, it is important to realise the 
simple character of the active agents in many such 
liquids. In the majority of the most successful 
remedies definitely used on account of their colloidal 
properties, the active agent is a metal, such as silver, 
mercury, or palladium, or a non-metal element, such 
as iodine or sulphur. More complex substances, such 
as quinine and cocaine, have also been used success- 
fully in the colloidal state, but not nearly to the same 
extent as the elements just mentioned. The reason is 
quite simple ; with only a limited number of investi- 
gators it is impossible to proceed as rapidly as may be 
desirable, and the remarkable results which have 
followed the use of elements in the colloidal state has 
naturally resulted in attention being concentrated on 
these elements. 

A great advantage which colloidal sols of elements 
possess over compounds is the facility with which their 
action may be studied. If a salt or other compound is 
administered there is always the chance of it under- 
going hydrolysis or ionisation in the blood stream or 
alimentary canal, thereby setting up complex reactions 
in which elements other than the one under investiga- 
tion are involved. For example, iron may be adminis- 



tered in the form of a carbonate which is converted 
in the stomach into chloride, and this, on dilution, is 
hydrolysed so that eventually there are formed both 
hydroxide and chloride of iron. If the iron were 
administered as an element, these complications would 
be avoided, and the investigator would be much more 
certain in drawing conclusions. Except in the colloidal 
form, it is impossible to administer elements in an 
active state apart from other elements necessary to 
bring them into solution, for no method of grinding 
has been discovered which will reduce the elements to 
so fine a state that they will remain in suspension in 
water for months without any tendency to deposition. 
The coarser product obtained by the most elaborate 
process of trituration is devoid of those properties 
which give colloidal sols their therapeutic value. 

The effect of the administration of certain elements 
in a colloidal state to persons suffering from certain 
pathological conditions is extremely interesting, partly 
on account of the progress of the recovery, and partly 
on account of the absence of complications such as 
occur when the same element is administered in 
another form. For example, iodine and mercury, as 
ordinarily used, are both unsatisfactory on account 
of their great toxic action. This is almost wholly 
avoided when these elements are administered in the 
form of colloidal sols. The remarkable fact that 
colloidal silver and iodine do not stain the skin, whereas 
the pharmaceutical preparations of silver and iodine 
do so strongly, is a further indication of the striking 
difference between colloidal sols and ordinary solutions. 

Widely as colloidal metal sols differ from the same 


metals as usually known and from their salts, such sols 
have a remarkably close resemblance to enzymes in 
their action on physiological products. The activity 
of both is greatly increased in alkaline solution up to a 
maximum which is followed by a reduction in activity 
with further increase in alkalinity. 

There is also a striking parallelism between the 
poisoning action of various substances (prussic acid, 
hydrogen sulphide, and mercuric chloride) on a metal 
sol and on an enzyme (p. 42). 

Recent researches on the action of various glands 
have also shown that the fluids they excrete are not 
only colloidal in character, but that in several instances 
they contain, as an essential constituent, some element 
which is not usually considered as an integral part of 
the organism. Thus, the dependence of the thyroid 
fluid on its iodine content has only been established 
within the past four years. In a similar manner the 
minute quantities of sulphur, phosphorus, and iron 
which are present in the animal organism are not 
adventitious. They play definite parts, and their 
absence or diminution results in a serious disturbance 
of function. Insufficient iodine in the thyroid gland 
induces cretinism and analogous diseases, an in- 
sufficiency of phosphorus accounts for certain nervous 
disorders, too little iron in the blood results in anaemia, 
and deprivation of sulphur is characteristic of rheu- 
matic subjects. 

The intense power of reaction possessed by ele- 
mentary sols is very striking. They can induce 
chemical reactions to occur which would otherwise 
require conditions of temperature and pressure quite 


unattainable in the human subject. Thus, metal sols 
have a catalytic action as powerful as platinum black, 
and can effect such changes as the union of hydrogen 
and oxygen in the cold, the oxidation of hydriodic acid 
by oxygen in solution, and the decomposition of 
hydrogen dioxide. 

The activity of some metal sols is so great as to be 
barely conceivable. Thus, platinum sol has marked 
catalytic properties when only 0-0000002 grain of the 
metal is present ! This intense power of promoting 
reactions among other substances and of being them- 
selves left free at the end of the reaction results in 
very small quantities of metal sols being capable of 
effecting changes which are wholly disproportionate 
to the amount of sol present. It also explains why 
changes which are of an extremely complex character 
when a catalyst is absent may be effected readily in 
the presence of an elemental sol, and, further, that the 
administration of such a sol will produce results in a 
short time which would require a long period if effected 
by means of a long series of successive reactions. 
Metal sols have the further therapeutic advantage of 
acting most rapidly in faintly alkaline solutions, so that 
when properly prepared they are not affected adversely 
by normal blood. 

Before a drug can exert its full therapeutic action it 
must be converted into the ionised or into the colloidal 
state. Unfortunately, an element in the ionised state 
is always associated with the corresponding ions of the 
salt from which it was produced. Thus, mercuric 
chloride, when ionised, is separated into mercury ions 
and chlorine ions, and the net electric charge of the 


system is neutralised. When an element such as 
mercury is administered in the colloidal state, however, 
it, and it alone, is introduced as an active agent, the 
charge on the particles is quite definite and their 
activity is correspondingly great. Consequently, there 
is much truth in the statement that a drug to be fully 
efficient must be in a colloidal state, or convertible 
into it in the body of the subject. 

The conversion of a colloid into the form required 
by the organism is most rapid when the sol is injected 
intramuscularly, but there is less pain and equally 
good (though slower) results by intravenous injections, 
and in many cases by oral administration. 

The use of specific sols in medicine is no universal 
" cure all," but just as the administration of pure 
chemicals, such as quinine hydrochloride, marked a 
great advance over the use of a crude tincture of 
cinchona bark, so the employment of certain elements 
in the form of sols marks a still further line of progress 
in the conquest of disease. 

Taking the chief colloidal sols which have been 
used medicinally, we may first mention several metal 
sols : 

Colloidal gold was first prepared in a sufficiently pure 
state for effective examination by Faraday in 1857, 
but it was known in the Middle Ages, though its most 
important properties were not realised. As early as 
1885, it was largely in use in the United States as the 
basis of a cure for dipsomania, but even then it was 
only one of a number of ingredients of a complex 
mixture whose manufacturer does not appear to have 
known much about the properties of the gold in his 


preparation, notwithstanding the statements in the 
advertisements of that day. 

Colloidal gold is characterised by the great differ- 
ence in its colour when it is prepared by different 
methods. As ordinarily prepared by reducing a 
slightly alkaline solution of gold chloride with formal- 
dehyde or phosphorus, it is an intensely red liquid, the 
particles of which are negatively charged, but by the 
addition of suitable electrolytes (aluminium salts), it 
is also possible to produce a blue solution with posi- 
tively charged particles. A colourless gold sol is 
produced if the electric field is too strongly negative 
or positive. Experiments by Garnet l on the refractive 
indices of colloidal sols of gold, silver, and copper show 
that the metal in each case is in suspension in the form 
of extremely minute spheres and that the different 
colours of gold sols are due to the particles of metal 
and not to any inherent differences in the nature of the 
dispersed particles. 2 

Colloidal gold sol is tasteless and non-poisonous, but 
the metal is readily precipitated by bases and salts, 
so that it is not easy to administer it satisfactorily. 
Moreover, the germicidal action of gold is very feeble 
(p. 73), so that its use in therapeutics is negligible. 
On the other hand, it is so easily prepared and is so 
highly sensitive that gold sol is chiefly used as a 
standard with which others may be compared. 

1 Phil. Trans., (A) 203, 1904, 385 ; and 205, 1906, 237. 

z According to T. Sherrer (Engineering, 1919, 488), colloidal gold 
and silver hydrosols, when examined by X-rays, show interference 
bands characteristic of crystalline solutions ; the interference bands 
of the hydrosols of silica and stannic acid show that these substances 
are sometimes crystalline and sometimes amorphous. Colloidal 
albumen, casein, starch, and cellulose appear to be always amorphous. 


Colloidal silver, containing 0-05 per cent of the 
metal in a colloidal form and not as a salt, is a clear 
cherry red liquid which possesses a marked oxidising 
action in addition to its power of coagulating colloids 
of opposite electric sign. 

The colour of the pure silver sol is largely dependent 
on the manner of its preparation and the presence or 
absence of minute quantities of electrolytes. Even 
the glass of the vessel in which the sol is prepared may 
affect the colour by yielding traces of soda, silica, or 
other oxide to the sol. When prepared under suitable 
conditions and properly " protected," colloidal silver 
sol is quite stable even in the presence of salts and of 
the normal constituents of the blood. Its destructive 
action on toxins is very marked, so that it will protect 
rabbits from ten times the lethal dose of tetanic or 
diphtheric toxin. Colloidal silver is prepared in the 
following forms to meet clinical requirements : 

(a) Aqueous solution, in bottles or ampoules. 

(b) Pasta, in glyco-gelatin base. 

(c) Ointment in lanoline base. 

(d) Suppositories and pessaries. 

Unlike certain organic compounds of silver, the 
colloidal metal is not organotropic and does not cause 
necrosis of the underlying tissues. Hence, it has been 
used for several months consecutively without staining 
the conjunctiva. 1 

Taken internally, the particles of colloidal silver are 
resistant to the action of dilute acids and alkalies of 
the stomach, and consequently continue their catalytic 
action and pass into the intestine unchanged. The 

* Brit. Med. Jaurn., Jan. 15, 1915. 


importance of this is obvious in such conditions as 
ulcerative urticaria and other forms of dermatitis sug- 
gestive of toxaemia, 1 bacillary dysentery, diarrhoea, and 

The use of collosol argentum in ophthalmic practice 2 
and in the affections of the ear and in nasal catarrh 3 
and its clinical effect by intravenous injection in 
septicaemia are reported in the medical journals. 4 

Colloidal silver has been used with marked success 
in the following cases, cited by C. E. A. MacLeod 5 : 

Septic and follicular tonsilitis, Vincent's angina, 
phlyctenular conjunctivitis, gonorrhceal conjunctivitis, 
spring catarrh, impetigo (contagious acne of face and 
body), septic ulcers of legs, ringworm of body, tinea 
versicolor, soft sores, suppurative appendicitis after 
operation (the wounds cleaned rapidly), pustular 
eczema of scalp and pubes, chronic eczema of meatus 
of ear with recurrent boils, and also chronic eczema of 
anterior nares, offensive discharge in case of chronic 
suppuration in otitis media, bromidrosis of feet, axillae 
and blind boils of neck. By injection : gonorrhoea 
and chronic cystitis (local), boils, epiditymitis. 

Sir James Cantlie 6 has found it particularly effective 
in cases of sprue, dysentery, and intestinal troubles. 
Being non-toxic, the dose can be increased from i to 2 
or more drachms twice or thrice daily. 

A. Legge Roe regards stable colloidal silver as a 
most useful preparation 7 in ophthalmic practice, and 
particularly in cases of gonorrhceal ophthalmia, puru- 

1 Brit. Med. J., May 12, 1917. Lancet, Feb. 3, 1912. 

2 Brit. Med. J., Jan. 15, 1917. 8 Brit. Med. J., Nov. 15,1913. 
8 Brit. Med. J., Dec. 15, 1917. 7 Brit. Med.J., Jan. 16, 1915. 
* Lancet, Feb. 16, 1918. 


lent ophthalmia of infants, infected ulcers of the cornea 
and hypopyon ulcer (tapping of the interior chamber 
and cautery, and other operative procedures being now 
rarely required, whilst if perforation does occur it is 
smaller and more manageable), interstitial keratitis, 
blepharitis, dacryocystitis, and burns and other wounds 
of the cornea. According to this authority, the great 
chemosis which usually accompanies the use of silver 
nitrate is avoided and, in his opinion, if colloidal silver 
were adopted in every case of purulent ophthalmia 
of infants " there would be no such thing as impaired 
sight or blindness from this cause." He has had many 
cases of interstitial keratitis in adults, in which the 
complete opacity of the cornea has become absolutely 
clear in from three to five months, and anyone who has 
had much experience of this disease in adults knows 
how often permanent impairment of sight results, and 
how long the treatment used to last, especially if 
irritants had been used prior to colloidal treatment 
The eye is kept under atropine or preferably scopola- 
mine, and the colloidal sol is dropped in three times a 
day, the eye being kept closed afterwards for five 
minutes. When all active symptoms have disappeared, 
and not until then if any opacity remains, yellow oxide 
or mercury ointment may be used ; but, if treated 
throughout as described above, this will rarely be neces- 
sary. In dacyocystitis, Dr. Roe recommends that 
" after probing, the sac should first be syringed out 
with saline solution and, after expressing any that 
remains, the sac should be filled with colloidal silver 
with the syringe. In cases of long standing this will 
not be sufficient ; the sac should be incised and plugged 


with ribbon gauze, and for about a week the sac should 
be dressed daily by inserting it into ribbon gauze 
soaked in 10 per cent solution of potassium bichromate, 
or the lining membrane of the sac should be scraped. 
The wound is then allowed to close and the collosol 
injections continued." 

T. H. Anderson Wells 1 used it intravenously in a 
case of puerperal septicaemia without any irritation of 
the kidneys and with no pigmentation of the skin. 
This physician has found that a series of intravenous 
injections, each of collosol argentum, every forty-eight 
hours produce no untoward effects and that recovery 
is rapid. 

Sir Malcolm Morris 2 has found that colloidal silver 
is free from the drawbacks of other preparations of 
silver, viz. the pain caused and the discoloration of 
the skin ; indeed, instead of producing irritation it 
has a distinctly soothing effect. It rapidly subdues 
inflammation and promotes the healing of the lesions. 
He has had remarkable results in enlarged prostate 
with irritation of the bladder, in pruritis ani and 
perineal eczema, and in haemorrhoids. It can be used 
in the form of suppositories whilst a solution is simul- 
taneously applied to the irritated skin. In bromidrosis 
in the axillae and feet it quickly gives relief. It causes 
a rapid disappearance of warts. Being non-toxic, it 
can be given internally in urticaria and other forms of 
dermatitis which are suggestive of toxaemia. In such 
cases, it is quickly beneficial. 

In ophthalmology, colloidal silver has now largely 
replaced silver nitrate. 

1 Lancet, Feb. 16, 1918. 2 Brit. Med. J., May 12, 1917. 


J. Mark Ho veil 1 has found colloidal silver beneficial 
for permanently restoring the potency of the Eusta- 
chian tubes and for reducing nasopharyngeal catarrh. 

Colloidal silver has also been used successfully in 
septic conditions of the mouth (including pyorrhoea 
alveolaris Rigg's disease), throat (including tonsilitis 
and quinsies), ear (including Menier's symptoms and 
closure to Valsava's inflation), and in generalised septi- 
caemia, leucorrhcea, cystitis, whooping-cough, and 

A preparation of colloidal silver which is opaque to 
X-rays has proved invaluable in certain diagnoses. 

J. MacMunn 2 has successfully used silver sol in cases 
of gonorrhceal prostatic gleet by injecting through an 
endoscope into the substance of the prostate gland. 

Collosol argentum has also proved useful in influenza, 
both as a prophylactic and for curative purposes when 
applied as a spray to the nostrils, for bathing the eyes, 
and as a gargle for the throat. 

B. Seymour Jones has used an intranasal spray of 
colloidal silver in a case of cerebro-spinal meningitis. 
He has also used colloidal silver with marked advan- 
tage in several cases of rhinitis and cedematous en- 
largement of the posterior ends of the middle and 
inferior turbinates without true hyperplasia. 

Colloidal mercury is quite free from the serious objec- 
tions to the less soluble mercury salts such as calomel 
the delayed and irregular absorption with conse- 
quent undesirable results of other preparations and, 
unlike the soluble mercury salts, it is only feebly toxic. 

1 Brit. Med. Journ., Dec. 15, 1917. 
1 Brit. Med. Journ., 1917, I, 685. 



S u 


With colloidal mercury, the diffusion is extremely rapid 
and chemical affinity low. Hence, the toxicity of col- 
loidal mercury (1-2000) is so low that doses of two 
teaspoonfuls may be taken twice daily or intravenous 
injections of 30 cc. may be given with impunity. 

Intravenous injections of colloidal mercury are pain- 
less, and this absence of pain is usual in the adminis- 
tration of colloidal preparations, and is due to their 
isomorphism with the colloidal lipoid and protein of 
the tissues and body fluids. Before the introduction 
of the arseno-benzene products, the routine treatment 
for syphilis was mercury and iodides, and undoubtedly 
many permanent and excellent results were obtained. 

In late syphilis, iodine is more effective than mercury, 
and, conversely, mercury is more effective than iodine in 
early syphilis. According to J. E. R. McDonagh, 1 this is 
due to the fact that mercury acts as an oxidising agent 
and that the process of oxidation is more effective in the 
early stages of syphilis in producing the death of the 
causal organism, whilst as a reducing agent it is more 
effective in the later stages. In most cases, the alter- 
nate injection of colloidal iodine and mercury is more 
effective than if either be given continuously. Accord- 
ing to J. E. R. McDonagh, 2 the first effect of injecting 
a suitable colloid is to break large protein particles into 
small ones and thus increase their activity by enlarging 
their surface area. In syphilis, there are many large 
particles to be broken up, hence the value of colloid 
sols. The injection of colloid sols also affects the state 
of oxidation or reduction of the system in which it is 
introduced, metallic sols increasing the oxidation and 

1 Prescriber, June, 1919, 118-120. * Brit. Med. J. t 1917, I. 648, 


non-metallic sols the reduction. Colloidal mercury has 
cured persistent relapsing malaria in a few days. 1 

Colloidal iron is the least irritating of all forms of 
iron, yet, according to Lyn Dimond, 2 it kills within six 
minutes such organisms as B.typhosus, B. coli communis, 
and various pyogenic cocci. The iron sol seems to have 
a definite elective bactericidal action upon such catarrh- 
causing organisms as the pneumococcus and various 
strains of the Micrococcus catarrhalis. Rapid relief 
follows the topical application of colloidal iron in cases 
of catarrh of the nose, larynx, or pharynx. 

It is also used by subcutaneous, intramuscular and 
intravenous injection in cases of extreme chlorosis, 
anaemia, erysipelas, and cellulitis. 

Iron is almost the only metal found in the animal 
organism which is also obtainable in a colloid state in 
the presence of water. The significance of the fact has 
not been sufficiently recognised. In the serum, the iron 
is probably present as a protein compound, the precise 
constitution of which has not been determined. Some 
authorities consider that the whole of the iron exists 
in the form of haemoglobin. The total iron content 
of the normal body does not exceed thirty-seven grains, 
and although several organic compounds of iron have 
been recommended they are by no means satisfactory, 
being either too feeble in action or too readily decom- 
posed in corpore and so rendered useless. Inorganic 
iron is held by many practitioners to be most efficient 
in the only true test of the value of an iron preparation, 
i.e. increase of haemoglobin in the blood. Haemoglobin 

1 G. Cremonese, Garr, D. Osp., 1918, 39, 427. 

2 Lancet. 1913, I, 1585. 


was at one time thought to be a definite compound, 
but its adsorption properties seem to show that it is 
largely colloid in character and consequently is specially 
amenable to the action of another colloid such as iron. 
Haemoglobin is electro-positive, and to increase its 
amount without disturbing the general characteristics 
of the serum any iron compound administered must be 
electro-positive when it enters the blood stream. For 
this reason, iron compounds (e.g. ferric chloride) which 
are electro-negative and act as coagulants should be 
avoided. The objection to iron carbonate and 
hydroxide lies in the fact that they are usually con- 
verted into ferric chloride or analogous compounds by 
the gastric juices. 

Colloidal iron, on the contrary, not being affected by 
these juices, is able to enter the blood stream in a satis- 
factory and therapeutically active form. Hence the' 
administration of iron in the form of a colloidal sol 
appears to be a simple means of increasing the amount 
of the protein compound in the serum, as this form of 
iron, when administered orally, is rapidly diffused in the 
stomach, and yet it is not absorbed in individual 
positions. It is found that the amino-acids formed 
during the process of digestion are readily able to absorb 
into their complex molecule a notable proportion of 
iron administered in the colloidal form, and from it 
to effect the synthesis of haemoglobin. 

Colloidal antimony has been used with remarkable 
and surprising results in the treatment of coccogenic 
skin disease, including deep abscesses, boils, and deep- 
seated impetigo. It has also been successfully used by 
intramuscular injection in bilharzia, leishmonnoris, 


granulama pupendi, ulcus molle serpiginosum, and in 
certain stubborn cases of gonococcal urethritis. 

Colloidal antimony has been used in conjunction 
with manganese with extremely good results in gono- 
coccic infections. In India, it has given very satisfac- 
tory results in Kala-azar, its administration in this 
disease being accompanied with less risk than that of 

Colloidal manganese has been used with remarkable 
and surprising results in the treatment of coccogenic 
skin disease, including deep abscesses, boils, and deep- 
seated impetigo. In superficial impetigo, chronic 
seborrhoeic eczema, and acute folliculitis it is of little 
value when used alone, but it gives excellent results 
when employed in conjunction with intramine. The 
rapidity of its action, 1 combined with the saving of 
dressings, render the use of this form of manganese 
very attractive in deep-seated coccogenic lesions. It 
is usually injected intramuscularly in amounts of 3 cc. 
every few days. In most cases, one injection is suffi- 
cient. Indeed, colloidal manganese differs from all 
other remedies used in the treatment of boils, insomuch 
as it is only occasionally that fresh boils make their 
appearance during the treatment, and these quickly 
subside without further trouble. 

E. W. Kirk 2 and Dr. W. Habgood 3 found colloidal 
manganese so good as to convince them that it should 
have a wider use in furunculosis and seborrhoeic eczema 
following wound infection, and W. E. Levinson 4 has 

1 J. E. R. McDonagh, Medical Press and Circular, Dec. 5, 1917; 
Sir Malcolm Morris, Brit. Med. Journ., April 26, 1918. 

2 Brit. Med. Journ., 1918, II, 377. 3 Brit. Med. Journ., II, 76. 
* Brit. Med. Journ., 1918, II, 160. 




I * 



confirmed Sir Malcolm Morris's 1 recommendation of 
colloidal manganese for boils. 

J. E. R. McDonagh 2 has also used intravenous injec- 
tions of 33 cc. of colloidal manganese with excellent 
results in cases of poisoning by sulphur compounds, 
including mustard gas (dichlorethyl sulphide). Three 
typical cases reported by Sir Malcolm Morris are, in his 
opinion, so remarkable as to demand publication. At 
first the collosol manganese (Crookes) was used in the 
form of a single solution. Afterwards it was employed 
in the improved form of two solutions, which were 
mixed in the syringe ; of this, much smaller doses 
(about one-half) suffice. 


" The patient, a medical man, came to me on Novem- 
ber 24th, 1917, with large, deep-seated boils on the 
hairy part of the face, which he believed to be an 
infection from a carbuncle in a diabetic patient, from 
whom he had contracted a septic whitlow. Culture 
showed that the micro-organism was the Staphylococcus 
pyogenes aureus, and an autogenous vaccine was pre- 
pared, with which he was inoculated on November 3Oth. 
By this time a boil on the right cheek had enlarged to 
the size of a Tangerine orange ; there was much cedema 
of the face and eyelids and great pain. On December 
6th pus was discharged and the pain relieved ; but 
during the next seven weeks boils continued to appear 
at intervals, usually in groups of four or five, on one 
or both sides of the face. By January I4th, eleven in- 
jections of vaccine had been given, antiseptic lotions 

1 Brit. Med. Journ., 1918, I, 446. 

* J. E. R. McDonagh, Medical World, 1918, p. 137. 


and ointments being also applied. On January 3ist 
the patient consulted me again and I advised the in- 
jection of collosol manganese. The first injection was 
given the next day. ' Improvement,' to quote from 
the patient's own notes, ' began on the third day 
afterwards. Subsequent boils, which continued to 
appear for a further fourteen days, were not painful, 
and many of them aborted without pus formation.' In 
all, four injections were given 1-5 on January 
3ist, 2-5 on February 5th, 3 on February 
I2th, and i on February 28th ; the first and 
second in the gluteus, the third and fourth in the flank. 
In the first three the old preparation was used ; in the 
fourth the new. By March 5th I was able to report 
' All clear/ From November 3oth to January 3ist, 
while the vaccine was being given, thirty-three carbun- 
cular boils appeared ; after the collosol manganese was 
begun there were only seven, the last appearing on 
February 2Oth, three weeks after this treatment was 
begun. The patient's general health also greatly 
improved ; he began to feel better within a week of 
the first manganese injection." 


" The patient was an army captain who was subject 
to acne. When the first collosol manganese injection 
(0-5 of the new preparation) was given on March 
I3th, he had been in hospital four months with facial 
boils and acute impetigo contagiosa of the same region. 
During that time he had had vaccine injections, and 
various antiseptics had been applied, without result. 


Another manganese injection (0-5 was given on 
March i6th, and a third (i on March igth. By 
this time all the lesions had cleared up." 


" I saw the patient, a lady, for the first time on 
February i6th. She had extensive follicular impetigo 
of the scalp, which began in the preceding October, 
and had gradually become more severe. When she 
came to me, she complained of great pain from small 
multiple deep abscesses. There was a good deal of 
oedema, and the posterior cervical glands were enlarged. 
On February i8th 1-5 of the old collosol man- 
ganese solution was injected. By February 22nd the 
lesions were beginning to clear up, the pain was nearly 
gone, and the general health distinctly better. A 
second injection (0-5 of the new preparation) 
was given, and a third (i three days later. By 
this time further improvement was manifest, and the 
patient was able to sleep. No further injection was 
required, and by March igth recovery was complete, 
the only trace of the disease consisting in small bald 
areas on the site of the lesions." 

Sir Malcolm Morris attaches much importance to 
the great improvement in the patient's general health 
observable in each case a few days after the first injec- 
tion, and the fact that although the injections were 
all intramuscular they were followed by no reaction. 

D. McFarland Livingstone has used colloidal man- 
ganese with great advantage in three cases of gonorr- 
hceal ophthalmia. The first was not of great severity, 
but the drug was satisfactory. In the second case, 


corneal ulceration had set in, but the eye healed 
rapidly. The third case was of the most virulent 
type, and the effect of colloidal manganese was most 
striking. Prior to treatment, both eyelids were greatly 
swollen and almost solid ; there was great tenderness 
and pain and the surrounding cheek was also red and 
swollen. On opening the lids, the cornea was found to 
be completely hidden by overlapping folds of cedema- 
tous bulbar conjunctiva. There was an abundant dis- 
charge of pus. The eye was bathed with warm boric 
lotion and argyrol was used every six hours. An in- 
jection of colloidal manganese was given intra-mus- 
cularly into the buttock. On the second day there was a 
slight improvement. On the third day there was slight 
pain ; on the fourth day a second injection of i cc. of 
colloidal manganese was given, and by the following 
morning all pain had ceased, all the swelling of the bulbar 
conjunctiva had completely vanished, the oedema had 
lessened, and the discharge was considerably reduced. 
The cornea was perfectly clear, and the eye was ap- 
parently out of danger. After one week from the 
first injection, a third and last injection of manganese 
was given, and after a further week the eyes had 
become normal, except for gumming of the eyelids 
after sleep. Dr. Livingstone reports of this case that 
" in a fairly wide and long experience in the treatment 
of gonorrhceal blenorrhcea it had never been my good 
fortune to witness such a dramatic change. No local 
measures of which I am acquainted would have brought 
about such a satisfactory termination." 

It is not suggested that undue importance should 
be attached to a single case, however striking, yet it is 




clear that such a good indication of what may be 
expected under similar conditions should not pass 

Colloidal manganese has also been used successfully 
in the case of toothache due to abscess. 1 

Colloidal copper sols are blue, red, orange, or green, 
according to the conditions under which they are 
prepared, and the agent used to stabilise them. 
Thus, if protalbinic acid followed by hydrazine 
is used for reducing copper sulphate, the sol is red 
or orange, whilst with protalbinic acid and sodium 
chloride Paal obtained green copper sols. Copper 
has a special action on the liver and is well known 
as a fungicide and as restraining the growth of the 
lower organisms and embryonic cells. In the form 
which has given the best therapeutic results, col- 
loidal copper sol is a dichroic liquid, blood red by 
transmitted light and muddy red by reflected light, 
which contains o-i per cent of copper as cuprous 
subhydroxide, protected by a combination of amino- 
acids, which per se have a very low physiological action. 
The solution is very stable, but should not be exposed 
unduly to the action of air or light, and for this reason 
the product is issued in hermetically sealed ampoules, 
each containing sufficient for one injection. 

It appears to be of use in some cases of cancer, and 
the dissipation of a nodule in a patient who had 
previously been operated on for scirrhus of the right 
breast (cancer) is reported. Results are in many cases 
satisfactory, particularly in the initial stages of the 
growth and in preventing recurrence after operation. 

1 D. A. Wood, Brit. Med. Joufn., 1919, 330. 


Where pain is present, great relief is obtained by the 
intravenous injection of colloidal iodine. If any 
streptococcus is present, injections of colloidal man- 
ganese should be given alternately with those of copper. 
In some cases where an improvement is manifested, but 
not maintained, injections of a reducing agent, such as 
pallamine (colloidal palladium) or intramine may be 
given alternately with copper or manganese, Inj ections 
of colloidal copper should always be given intramuscu- 
larly, preferably in gluteus medius. The dose is 3 cc. 
and the injection is preferably given on the first, fourth, 
seventh, and twelfth days and then once a week. 
Treatment should be continued until all symptoms have 
completely disappeared, after which one injection per 
month should be continued for about a year. 

The use of colloidal copper injected intravenously 
can aggravate boils if administered in large doses ; 
in smaller quantities and injected intramuscularly it 
has the opposite effect, but is far inferior to colloidal 
manganese for this purpose. 

In malignant disease the intramuscular injection 
of copper has proved beneficial, the metal having 
been shown to be present in the growth within twenty- 
four hours of the injection. Merchel de Gers and 
others 1 have stated that colloidal copper exerts 
an inhibitive action on all cell-metabolism and it 
has been used extensively on the Continent in the 
treatment of cancer. In this connection, it is impor- 
tant to note that cases of cancer in which copper 
can be shown to be present in the growth are certainly 
the ones which are most amenable to treatment. The 

1 Med. Press, 1912, II, 26 ; 1913, I, 87. 


difficulty lies in causing the copper to penetrate to the 
periphery of the cancer. 

Pessaries of colloidal copper in glyco-gelatin have 
proved serviceable for uterine fibroids. 

Luton l refers to the value of the salts of copper in 
tuberculosis ; its various forms yield more or less 
rapidly to the treatment when begun regularly. The 
existence of high fever is regarded as an obstacle to the 

Colloidal platinum sol has been extensively used in 
promoting various chemical reactions. It appears to 
be too powerful for use in medicine, but has been 
employed to a limited extent for the same diseases as 
colloidal silver. 

Dr. A. G. Auld has obtained encouraging results with 
colloidal platinum in case of pyrexia, e.g. subacute 
pleuritis and pneumonic conditions and protracted 
paratyphoid fever. He found that colloidal silver 
acted even more intensely than the year-old platinum 
colloid previously used, and as it is less drastic it is, in 
every way, preferable. 

Colloid palladium oxide has been applied successfully 
in the treatment of obesity by injecting it hypoder- 
mically into the fatty areas. 2 

Colloidal palladium is a reddish liquid of a peculiarly 
active character 

A. C. King-Turner 3 has used colloidal palladium 
(pallamine) with good results in epilepsy, the results 
of injecting each patient intramuscularly with 0-5 cc. 

1 Prov. Med., Dec., 1912. 

8 Brit. Med. Journ., 1918, I, 195. 

3 M. Kauffmann, Munch. Media. Wochenschr, 525, 1913. 


of " pallamine " at intervals of three days being most 
marked and encouraging. To cite three cases : l 

" H. G., male, aged forty-five, suffering from epilepsy 
and of doubtful traumatic history, had an average of at 
least four fits weekly. These fits were of a very violent 
nature, the convulsion stage lasting on occasions for 
an hour, followed by stupor, confusion, and excitement. 
Since the three injections, only one fit has occurred in a 
fortnight, and that of a mild nature, lasting only thirty 
seconds. The patient feels greatly improved in general 
health, is less morose, more conversant, expressing 
himself more lucidly, and is very grateful for the 

M. A. L., female, aged fifty-three, an epileptic of 
thirty years' standing, with an average of six fits per 
week of a very violent nature. Since injection, three 
weeks ago, no fit has occurred, but she has had a few 
sensations. She is now very placid, well behaved, and 
much better in every way. 

M. A., female, aged sixteen, congenital epilepsy. 
She had seldom less than three or four fits per day. 
Since injection, three weeks ago, only four fits have 
occurred. She is much brighter, greatly improved in 
general health, and has now great hopes of being dis- 
charged from the institution, recovered. In two cases 
where manganese sol was injected after pallamine, a 
fit resulted, showing that careful selection of the 
appropriate metal is necessary." 

Like colloidal platinum, pallamine is a very powerful 
catalyst, and such strongly combined organic sub- 
stances as nitro-benzol, and numerous acids, aldehydes, 

1 Brit. Med. Journ., 1918, II, 255. 


ketones, diketones, and nitriles are readily reduced by 
passing hydrogen through them, if a little colloidal 
palladium is present and the products are kept neutral 
by the addition of sodium carbonate. 

Sols which are not normal constituents of the body, 
e.g. mercury, arsenic, are liable to be toxic, but mercury 
is less toxic than arsenic, as it has less affinity for nerve 
tissue, and the colloidal preparations are quite unlikely 
to be dangerous in the hands of medical men. It is, 
of course, important that they should be prescribed 
with due care as, otherwise, oxidation may occur where 
reduction is desired, or vice versa, but the risk of 
serious results to the patients is far less than when 
certain crystalloid remedies or tinctures, etc., are used. 

Colloidal nickel has been used in meningitis. 

Of the non-metal elements, the most widely used are 
iodine and sulphur. 

Colloidal iodine may be obtained in four forms: 
(i) aqueous, and (ii) oil, (in) ointment, and (iv) sup- 
positories with gly co-gelatin base. The aqueous colloid 
(i in 500) contains the element in its most active form, 
and is suitable for administration in all cases in which 
iodine or an iodide is indicated. Its action is more 
gradual, but more certain, than that of iodides, and 
there is complete avoidance o f " iodism " and nausea. 

The whole of the colloidal iodine is absorbed, 
whereas 85 per cent or more of the ordinary iodides 
administered are excreted within twenty-four hours. 

When injected intravenously, the action of colloidal 
iodine is more rapid, and as much as 300 c.cs. has been 
injected with impunity in cases of pyaemia, and also 
to produce softening of fibrous tissue, thus showing 


its absolute non-toxicity. In itself, colloidal iodine is 
only slightly parasitotropic and bacteriotropic, but 
micro-organisms are very greatly influenced by its 
action, and it greatly increases the effect of a subse- 
quently administered remedy. 

Colloidal iodine is also indicated in syphilis by prior 
injection, and also by internal administration, and in 
cancer by intravenous injection. 

In rheumatism, a piece of flannel soaked in colloidal 
iodine attached to the positive pole of a battery and 
applied as near as possible to the affected area has been 
successful. It has also been used beneficially as a 
spray in bronchial and nasal catarrh and internally in 
recovery from alcoholism. 

Colloidal iodine oil (3 per cent) is very useful for 
eczema and other forms of affections and abnormal 
conditions of the skin. On application, the iodine 
particles penetrate the pores of the skin without stain- 
ing the epidermis, the latter being kept supple and 
soft by the hydrocarbon oil in which the colloidal 
iodine is exhibited and stabilised. Thus, the staining 
and hardening effects of alcoholic solutions of iodine, 
such as tincture of iodine, are avoided. 

In some cases of bad chilblains 1 colloidal iodine 
oil rubbed in four or five times a day caused every 
trace of the condition to disappear in four days. 
Equally valuable is this colloid in severe cases of 
trench feet with ulceration, and in many cases of 
Charcot's bedsores which are so troublesome a com- 
plication of spinal injuries in military hospitals. In 
the earlier inflammatory stages of lupus erythematosus, 

1 Brit. Med. /., May 12, 1917. 






o ^ 


before atrophy has supervened, it is far more suitable 
than the ordinary form of the drug because of the 
absence of irritation. Similarly, it is preferred for 
internal administration in the later stages of syphilis, 
because there need be no fear of iodism. Parasitic 
affections show a striking amenability to this remedy. 
In a case of dhobie's itch, in which the disease had 
spread from the groin and invaded the trunk, legs, and 
arms, under the quite painless application of colloidal 
iodine oil the extensive lesions all cleared up in three 
weeks ; with ordinary remedies, the case would un- 
doubtedly have been more protracted, and the treat- 
ment would inevitably have put the patient to a good 
deal of pain. 

Colloidal sulphur (i per cent) has proved invaluable 
in cases where there is a deficiency of this element in 
the system. The value of sulphur has long been known, 
but the forms in which it is usually administered are 
crude. It has been necessary to employ excessively 
large doses of an insoluble form of sulphur or to 
administer " Harrogate water," or some equivalent 
and unpleasant preparation of hydrogen sulphide. 
There is little doubt that an insufficient amount of 
available sulphur in the system impairs the action of 
the liver, with consequent production of intestinal 
poisoning (constipation, headaches, arthritis, etc). 
Externally, in the form of ordinary sulphur ointment, 
the element is in far too coarse a state to penetrate 
the epidermis efficiently, whereas in the colloidal form 
it does so readily. Colloidal sulphur ointment (5 per 
cent) is a brown paste ; when this is rubbed on the 
skin its colour rapidly disappears owing to the penetra- 


tion of the sulphur into the skin, the colourless disperse 
medium remaining behind. This marked distinction 
between the behaviour of colloidal and ordinary 
sulphur is obvious to every one who has compared 

Colloidal sulphur is extremely active, readily com- 
bines with protein, and is entirely absorbed in the 
stomach. The products of this combination are 
rapidly taken into circulation, and those parts of the 
organism for which sulphur is necessary are thus 
supplied. Ordinary sulphur is not absorbed in the 
stomach at all, and passes practically unchanged into 
the intestines. 

A very interesting property of colloidal sulphur sol 
is its power when taken internally of completely 
deodorising the faeces, and thus acting in precisely the 
reverse manner to ordinary sulphur. The importance 
of this in phthisis, malignant disease, etc., is obvious. 
In many cases of rheumatism and neuritis, and even 
in " arthritis deformans," relief has been rapidly ob- 
tained by its internal administration. In acute rheu- 
matism, the intravenous injection of colloidal sulphur 
has proved beneficial. 

Colloidal sulphur baths have been of service in 
rheumatic conditions and skin affections. The colloidal 
sulphur content in the bath is far greater than that of 
natural sulphur water, and as the bath contains no 
impurities or free sulphuretted hydrogen, it is free from 
the many objections associated with the use of natural 
sulphur waters. 
Sir Malcolm Morris 1 has found that among the 



affections in which colloidal sulphur is beneficial are 
various forms of acne (including acne rosacea and 
seborrhcea), generalised dermatitis, acute psoriasis, 
and painful fibrositis, whether of connective tissue, of 
muscle, or of joints. Baths medicated with this 
colloid are, in his experience, at once soothing and 
quickly curative. 

Colloidal sulphur increases tolerance to mercury in 
syphilis and enhances its efficacy. It has also been 
recommended for use by subcutaneous injection in 

Sulphur can be administered as a simple sulphur sol 
or as a complex colloid, di-ortho-amino-thio-benzene 
(intramine) as prepared by J. E. R. McDonagh. These 
differ somewhat in their action, but for the cases 
previously mentioned either form may be used. 

Colloidal arsenic (0-2 per cent) in doses of 2 cc. has 
an extraordinary effect in pernicious ansemia and 
herpes deformans. 

In influenza, Capitan 1 obtained cures in 50 per cent 
of otherwise hopeless cases with doses 6-9 cc. of colloidal 
arsenic and the same volume of colloidal silver. The 
colloidal arsenic contains about 4 mgm. per cc. of 
arsenic, and the colloidal silver 2 mgm. per cc. of silver, 
the solutions being given intramuscularly or intra- 
venously. The number of injections varied according to 
the effects produced, from 3 or 4 to 6 or 7 in prolonged 
cases. In very severe cases, 6 cc. of colloidal arsenic 
and 3 cc. of silver were injected intravenously at once, 
and twelve hours later the same dose was given 
intramuscularly. The dose was repeated next day if 

1 Bull. Acad. de mid., Par., 1918, 3* Ser., 80, 388-93. 


the patient's state remained grave. If there was 
obvious improvement, a single intramuscular injection 
of 9 cc. of arsenic and 6 cc. of silver was given. Patients 
who recovered after one or two injections showed a 
complete change in their general condition ; the 
prostration, coma, and delirium disappeared, the 
temperature fell rapidly to normal, and the pneumonia 
resolved without delay. Apart from a little headache 
and nausea, no bad effects were produced. Intramus- 
cular injection of stannic oxide in colloidal suspension is 
advocated by Netter, 1 who has used them in 139 cases, 
92 of whom were children and 47 adults. The injections 
were given for several days in succession and appeared 
to shorten the duration of the disease, diminish its 
gravity, and reduce the mortality. The mechanism of 
the action of stannic oxide is not clear, as the bacteri- 
cidal power of tin is much less than that of silver, 
although Netter has found colloidal silver much less 
effective than stannic oxide in such cases. Witte 2 
recommends the rectal injection of a 2 per cent solution 
of collargol 3 from two to four times daily as long as the 
fever lasts, the patient being given 10 cc. in each 
injection. The treatment should be begun as early as 
possible, especially in the age-period in which the 
mortality is highest, namely, from twenty to forty. 

The simultaneous presence of a lipoid or colloidal 
protein appears to be essential to the proper reaction 
of arsenic. Thus, salvarsan per se has little action on 
Spirochceta pallida, which can move readily for some 

1 Netter, A., Bull. Acad. de mtd., Par., 1918, 3 e Ser, 80, 427-36. 

2 Witte, F., Deutsche med. Wochenschr., Berl. u. Leipz., 1918, 44, 

3 Collargol is a silver sol. 


hours in a solution of salvarsan. Yet the introduction 
of a little serum or digested protein will cause their 
immediate death. Organic arsenic compounds cause 
rapid sterilisation of the blood stream and disappear- 
ance of spirochaetes, but, owing to rapid elimination, 
the arsenic is unable to reach every spirochaete or its 
spore, and it is for this reason that the intramuscular 
or subcutaneous route is sometimes chosen as giving 
slower absorption and consequently slower elimination 
and more prolonged action (Harrison). The dis- 
advantage of this method is the pain usually caused. 
Colloidal arsenic is not so easily eliminated and may 
therefore be administered by the longer route. 
Its low toxicity, combined with the small dosage 
required, reduces the risk of its retention to a 

Colloidal oxides do not prove to be so satisfactory as 
the corresponding metals, though Colloidal alumina 
(gel) ( Eng. Pat. 104, 609) has shown excellent as- 
tringent effects in various kinds of diarrhoea and is less 
toxic than the bismuth compounds usually adminis- 
tered in such cases. 

Various alkaloids have been prepared in the colloidal 
state and have been used in medicine. The colloidal 
state is the ideal condition for the administration of 
alkaloids ; in it they are isotonic with the colloidal 
protein of the body fluids, and until this condition has 
been reached the full physiological action of the drug 
is not complete. The two most important of these 
alkaloids are quinine and cocaine. In the usual 
quinine solutions, time is wasted converting the alkaloid 
to this state and there is frequently considerable upset 


of the conditions regulating the blood and tissue cells. 
Thus, when an acid quinine solution is injected intra- 
venously, precipitation at first occurs, and the quinine 
is rapidly taken up again by the serum as a colloidal 
sol, but, in this process, the normal condition of the 
serum is destroyed. When colloidal quinine, which is 
faintly alkaline, is injected, no precipitation can occur, 
and consequently there is no upset of the normal 
condition of the blood. 

Colloidal quinine sol appears to be free from the chief 
drawbacks of quinine salts. As the latter, as well as 
the colloid, are readily decomposed in corpore, much 
more research is required before much can be said as to 
the real action of quinine. Curiously, colloidal quinine 
has no action on the parasite of malaria. 1 

Colloidal cocaine is peculiarly difficult to prepare 
and little is therefore known of its value as a local 

Colloidal combinations. The colloidal elements have 
usually been employed singly. This is important 
as the improper combination of colloidal sols may 
result either in an inert substance or in the production 
of conditions precisely the opposite of what is intended. 
For instance, A. C. King-Turner 2 has found that 
whilst the administration of colloidal palladium is 
helpful in epilepsy, yet subsequent administration of 
colloidal manganese induced further fits. On the other 
hand, suitable mixtures of colloidal elements have 
great possibilities, which are, as yet, only dimly realised. 
For instance, a mixture of colloidal manganese and 
iron can be prepared in an entirely stable form, and 

1 Stroud, Lancet, 1917, II, 911. * See pp. 97, 98. 


whilst the therapeutic properties of such a mixture 
have not been thoroughly ascertained, it appears that 
it not only possesses the remarkable properties of 
colloidal manganese and iron, when administered 
separately, but also has an additional effect, the nature 
of which requires further investigation. 

Complex colloids, such as gelatin, gum-acacia or the 
protein colloids, are injected intravenously in cases 
where it is desired to prevent undue loss of the saline 
constituents of the serum. Such colloids adsorb these 
crystalloids, retaining them in the blood-vessels, 
raising the osmotic pressure, expelling the toxins and 
generally reducing the effects of shock. After severe 
haemorrhage, both the colloidal and the crystalloidal 
constituents are deficient, and an injection of a complex 
colloid mixed with a hypertonic saline solution is the 
most efficacious restorative. If the saline is adminis- 
tered alone, much of it is rapidly excreted and lost. 
The simultaneous introduction of a suitable colloid 
ensures the adsorption of the saline matter and ensures 
its efficacy. Under normal conditions, there appears 
to be a considerable proportion of a crystal-colloidal 
complex in the body-fluids and for the retention of 
health a sensitive or labile equilibrium between the 
crystalloid and colloidal contents must, therefore, be 



THE form in which colloidal sols are employed has, 
naturally, a considerable influence on their effect. 
Several German preparations, placed on the market by 
British merchants, have given disappointing results 
because those physicians who employed them were 
insufficiently well acquainted with the nature of 
colloidal sols. Thus, for the purposes of ordinary 
chemical experiments, sols which have been evaporated 
to dryness and redissolved in water immediately before 
use are often convenient, but for the much more severe 
conditions of medical use such dried sols have proved 

Again, it is comparatively easy to prepare sols 
which will meet the ordinary requirements of the 
chemical lecturer, but such crude preparations are 
usually too unstable for medical purposes, or their 
stabilising agent or other constituents bring about un- 
desirable complications in the patient. It is, therefore, 
of the greatest importance that the colloids used by 
physicians should be prepared with special skill and 
care. Many samples which have been examined show 
great variations according to the sources from which 
they have been obtained, but it is satisfactory to be 
able to state that the preparations to which special 



reference has been made in this volume have invariably 
proved satisfactory when tested. 

There is, in some quarters, an idea that colloidal sols 
are too unstable to be of real value in pharmacy 
This is undoubtedly true of the crude preparations 
made by those who have not the necessary knowledge 
and skill, but it is emphatically false when applied 
to the preparations to which reference has already 
been made. 

There is also a disposition on the part of a small 
number of recent writers to confuse ideas of the differ- 
ence between colloidal elements and complex organic 
compounds which may be used either in a colloidal 
state or in the form of a true solution. This is an 
unfortunate attitude, as there is no necessary in- 
compatibility between the two classes of remedies. 
The excellent work of Ehrlich and his associates has 
had most remarkable results. It has clearly shown a 
line of attack which is likely to prove of still further 
value in the conquest of syphilis and allied diseases. 
On the other hand, it cannot be denied that the use of 
arsenic in a highly poisonous form in association with 
an organic complex which is intended to neutralise its 
toxic action is fraught with risks which, at present, 
appear to be much greater than the use of colloidal 
elements of very low toxicity. 

One unfortunate result of the use of improperly made 
colloidal sols has been the publication of a few state- 
ments in which the use of colloidal sols as remedies is 
condemned in general terms. If the origin of these 
statements is traced, it will be found that they have 
been made by those who have insufficient knowledge 


of colloids and have not made the necessary tests 
before jumping to conclusions, or they relate to colloidal 
sols of low activity, or to those which are not isotonic 
with serum and other body-fluids. 

Obviously, any conclusions based on such imperfect 
data should be regarded with grave suspicion ; they 
are certainly inapplicable to the colloids, mentioned in 
the foregoing pages, which have been used with such 
highly satisfactory results. 

No one with sufficient knowledge of colloidal sub- 
stances would claim that all drugs should be adminis- 
tered solely in this form. There are, in fact, many 
crystalline compounds which are invaluable for special 
purposes. Thus, there is, in health, a definite equi- 
librium between the saline (or crystalloid) and the 
colloidal content of the body-fluids which must be 
restored when it has been disturbed as the result of 
wounds or some bacterial or other disease-producing 
agency. Under normal conditions, the cells and serum 
are colloidal sols which retain 07 to 0^9 per cent of 
crystalloid or saline matter. 1 When the saline content 
is reduced below the lower of the limits just mentioned, 
the administration of a hypertonic crystalloid solution 
is usually indicated. If, on the contrary, an excessive 
amount of colloidal sol is present, the appropriate 
remedy may consist either (i) in raising the concentra- 
tion of the crystalloids by the administration of a 
saline, or (ii) in precipitating the foreign colloid by 
means of another colloidal sol of the opposite electric 
sign. The use of salines is well known, but the dis- 
covery of artificially prepared colloids which are stable 

1 B. Moore, Nature, 1919, 131. 


when in the human organism is, however, so recent and 
the results obtained from their administration are so 
remarkable that it seems desirable in the interests of all 
that their general characteristics should be set out 
briefly and clearly in order that still further progress 
may be made in the utilisation of colloids both in 
health and disease. 


Abscesses, 93, 95 
Acid, amino, 60, 89 

carbolic, 67, 68 

gallic, 25 

lysalbic, 7 

nucleinic, 28 

protalbic, 7 

tannic, 25 

Acne of the face and hands, 83, 

" Activated sludge " process, 31, 

3 2 

Activity of sols, 57 
Adsorption, selective, 2, 3, 107 
Agar, 12, 13, 70, 71 
Agglutination, 15 
Agglutinins, 39, 40, 41 
Air, action of, at seaside, 3 1 
Albumen, 7, 12, 23, 25, 26, 43, 

46, 81 

Alcoholism, 100 
Algae, unicellular, 13 
Alimentary tract, 28, 42 
Alkaloids, colloidal, 105 
Alumina, colloidal, 105 
Aluminium, colloidal, 73 

hydroxide, colloidal, 1 2 
Alveolaris, pyrorrhoea, 86 
Amino-acids, 60, 89 
Amoebae, 13 

Anaemia, 78, 88, 103 
Angina, Vincent's, 83 
Aniline blue, colloidal, 12 
Animal fluids, 21 

organisms, 1 3 

structure, 2 
Ani, pruritis, 85 
Antimony, colloidal, 73, 89-90 

sulphide, colloidal, 1 2 
Anti-toxins, nature of, 39, 40 
Appendicitis, suppurative, 83 
Aqueous phase, 46 
Argyrol, 94 

Arrhenius, S., 41 
Arsenic, 49, 109 

colloidal, 99, 103-105 

Arsenic, sulphide, colloidal, 12 

Arsenious acid, colloidal, 73 

Arseno-benzene, 87 

Arthritis, 101, 102 

Assaying sols, 56-66 

Asses' milk, 22 

Assimilation, 2 

Atropine, 84 

Atrophy, 38, 101 

Auld, A. G., 97 

Axillae, bromidrosis of, 83, 85 

Bacillus coli communis, 70, 71, 

tuberculosis, 7 1 

typhosus, 88 
Bacteria, i, 17, 36 

action of agglutinins on, 39, 

colloidal nature of, 15, 17, 68 

destruction of, 38, 68 

penetration -of cell walls by, 

propagation of, 38 

" protection " of, 41 

sensitiveness of, 39 
Bancroft, 35 

Baths, medicated, 103 

sulphur, 102 

Bed sores, Charcot's, 100 

Bilharzia, 89 

Bismarck, brown, colloidal, 1 2 

Bismuth, colloidal, 12, 73 

Black background, 58 

Bladder, disease of, 28 

Blenorrhrea, gonorrhosal, 94 

Blepharitis, 84 

Blood, carbon dioxide in, 26 

corpuscles, 26, 27 

nature of, 27 

oxygen in, 26 

serum, 40, 5 ! 
Body fluids, 44, 109 

colloidal state of, 37, 49 

viscosity of, 2 5 
Boils, 83, 90, 91, 96 



Bordet, J., 41 

Boric lotion, 94 

Bromidrosis of the feet, 83, 85 

Brownian movement, 5, 57 

Burns, 84 

Burton, 9, 10 

Buxton, 25 

Cadmium, colloidal, 73 

sulphide, colloidal, 12 
Cancer, 95, 96, 100 
Cantlie, Sir James, 83 
Capitan, 103 
Caramel, 13 

Carbolic acid, 67, 68 
Carbon dioxide in blood, 26 
Carbuncle, 91 
Casein, 7, 64, 8 1 

digestion of, 23 

in milk, 22 

Catalytic action of colloids, 79 
Catarrh, 83, 86, 88, 100 
Cells, action of salts on, 24, 25, 

embryonic, 95 

growth of, 25 

nature of, 25 

reactions in, 24 

selective permeability of, 24, 

structure of, 2, 23 

synthetic, 23 
Cellulitis, 88 
Cellulose, 81 
Cerebro-spinal fluid, 6 1 

meningitis, 86 

Cerium hydroxide, colloidal, 12 
Chadwick, Sir Edwin, 33, 34, 37 
Chambers, 23 
Charcot's bed-sores, 100 
Charge, electric, on a sol, 9 
Cheese, digestion of, 23 
Chemical action and electrical 

phenomena, 8 
Chilblains, 100 
Chloroform, colloidal, 13 
Chromium hydroxide, colloidal, 


Cinchona bark, 80 
Cleanliness, importance of, 33 
Cobalt, colloidal, 73 
Cocaine, colloidal, 76, 105, 106- 


Coccogenic skin disease, 89, 90 
Cod liver oil, emulsions of, 46 

Collins, Sir Wm., 38 
Colloidal metals, electric charge 
of, 70 

germicidal power of, 68, 73 

nature of, 69 

sols, precipitation of, 13-15 
protection of, 1 5 

particles, action of electric 
current on, 1 1 

activity of, 1 8 

calculation of electric 

charge, 9 

double electric layer of, 10 

electric charge on, 7, 12, 13 

oscillation of, 5, 18 

rate of movement, 1 3 

size of, 5, 20 

volume and surface area, 


remedies, 76-107 

sols, action of radiations on, 

precipitation of, 13-15 

protection of, 1 5 

state, denned, 4 
Colloidogens, 7 

Colloids, absorption spectra, 20 

accidental use of, 45 

action of air on, 65 

alkalies on, 78 

dust on, 65 

heat on, 65 

light on, 65 

membranes on, 43 

adsorption of, 68 

advantages for internal use, 

Colloid and crystalloid, equi- 
librium between, 107 

Colloids and digestion, 2, 42- 

and solutions, distinction 
between, 16 

appearance of, 57 

characteristics of, 7 

coagulation of, 50 

colour of, 19 

colour, variations of, 20 

complex, 107 

determination of activity, 

dosing of, 53, 79 

effect of serum on, 65-66 
time on, 65 

equilibrium of, 5 5 


Colloids, German, 50 

hydrolysis of, 43 

injection of, 34, 54, 80, 85, 
88, 91, 93, 96, 97, 99, 103, 
104, 1 06 

intensity of reaction, 78 

mixed, 106 

nature of, 1-20 

preparation of, 51, 54 

properties of, 1-20 

protection of, 5 1 

protein, 107 

settling time of, 65 

stabilising, 5 5 

stability of, 50, 51, 55, 66 

under ultra-microscope, 57 

unstable, 51, 54, 60, 108 
Colour of colloids, 19 
Common salt as colloid, 6 
Compounds, dissociation of, 9 
Condensation, 53, 54 
Congenital epilepsy, 98 
Conjunctiva, 82 

oedematus, bulbar, 94 
Conjunctivitis, gonorrhoeal, 83 

phlyctenular, 83 
Constipation, 101 

Copper, colloidal, 12, 73, 81, 95- 

hydroxide, colloidal, 12 
Cow's milk, 21, 22 
Corneal ulceration, 94 
Corrosive sublimate, 72 
Cretinism, 78 

Crookes, Henry, 52, 68, 69, 70, 

73. 74 

Crystalloids under ultra-micro- 
scope, 58 

and colloids, equilibrium be- 
tween, 107 

Cuvette, 59 
Cystitis, 83, 86 

Dacryocystis, 84 

Deltas, formation of, 33 

Dermatitis, 85, 103 

Dextrin, 64 

Dhobie's itch, 101 

Dialysis, n 

Diarrhoea, 105 

Diatoms, colloidal, 13 

Diffusion, n, 28 

Digestion and colloids, 2, 42-44 

nature of, 26, 43 

Digestion and colloid products, 
action of colloidal iron on, 89 

Dilute solutions, germicidal 
power of, 69 

Diphtheria toxin, 40 

Diplococcus, 71 

Dipsomania, 80 

Disease, origin of, 36, 37 

Disease-producing organisms, 
evolution of, 38 

Disinfectants, colloidal, 67 

Disperse phase, 4, 46 

Dispersion medium, 4, 51 

power of soaps, 34 
Dissociation of salts, 9 
Donnan, 43 

Double electric layer, 10 
Drainage, importance of, 33 
Drugs, action of, 79 

dose and effect, 47 

erroneous results from intro- 

duction of, 17 

ionisation of, 79 
Dyes, 7 
Dysentery, 83 

Ear affections, 83 
Ebonite, electrification of, 8 
Eczema, 83, 85, 89, 90, 100 
Ehrlich, 49, 109 

Electricity, influence on animal 
organisms, 13 

use of, as a remedy, 1 3 
Electrification of colloidal par- 
ticles, 7 

Electrolytes, 6, 7, 10 
Electronegative colloids, 7 
Electropositive colloids, 7 
Embrocations, 46 
Emetics, 47 
Emulsifying agents, 46 
Emulsion, 39, 46 
Emulsoids, 6, 23, 25 
Endoscope, 86 
Enzymes, 17, 42, 78 
Eosin, colloidal, 12 

solution, 62 
Epiditymitis, 83 
Epilepsy, 97, 98, 106 
Erysipelas, 88 
Erythematous lupus, 100 
Eustachian tubes, 86 
Faeces, deodorising, 102 
Faraday, 80 



Ferments, 42 

Ferric hydroxide sols, 12, 27 

Fever, paratyphoid, 97 

Fibrositis, 103 

Fibrous tissue, 99 

Field and Teague, 40 

Fish-agar, 74 

Fluid, cerebro-spinal, 61 

gland, 78 

thyroid, 78 
Follicular tonsilitis, 83 
Folliculitis, acute, 90 
Foot-and-mouth disease, 
Formalin, 68 

Formic aldehyde, 54 
Fuchsine, colloidal, 54 
Furunculosis, 90 

Gallic acid, 25 

Galvanotropism, 25 

Garnet, 81 

Gelatin, 4, 6, 13, 21, 22, 23, 24, 

28, 39, 64, 107 
Gels, denned, 14 

formation of, 14 

haemolysis of, 27 
Germicides, colloidal, 67 
Gland, prostate, 86 
Glands, 78 

Glass, electrification of, 8 

Gleet, 86 

Globulin, colloidal, 12 

Glue, 64 

Gluteus medius, 96 

Glyco-gelatin, 97 

Glycogen, 48 

Glycophosphates, 48 

Gold chloride, 54 

colloidal, 9, 19, 54, 73, 80-8 1 

metallic, 3 

number of sols, 63-65 
Gonococcal urethritis, 90 
Gonococcus, 71 
Gonorrhoea, 83 
Gonorrhoea! blenorrhoea, 94 

conjunctivitis, 83 

ophthalmia, 83, 93 

prostatic gleet, 86 
Graham, Thomas, 3, 16 
Granulama pupendi, 90 
Graphite, colloidal, 73 
Gum acacia, 21, 24, 107 

arabic, 2 1 , 64 

Gutbier and Resenschack, 20 

Habgood, W., 90 

Haematin, 16 

Haemoglobin, 12, 26, 27, 43, 88, 


Haemolysis, 27 
Haemorrhage, 107 
Haemorrhoids, 85 
Harrison, 105 
" Harrogate water," 101 
Headaches, 101 
Henri, 26 

Herpes deformans, 103 
Hewin and Mayen, 19 
Hewlett, R. Tanner, 71 
Histone, 25 

Hoffmann, violet, colloidal, 12 
Homoepathists, 53 
Hovell, J. Mark, 86 
Human milk, 21, 22 

system, action of radiations 
on, 19 

Hydrogen sulphide, 78 
Hydrolysis, 53, 54, 76 
Hygienic uses of colloids, 29 
Hypertonic salt solution, 107, 

Impetigo, 83, 90, 92 

Indigestion, 44 

Indigo, colloidal, 12 

Influenza, 86, 103 

Injection of colloids, 34, 54, 80, 

85, 87, 88, 91, 93, 96, 97, 99. 

103, 104, 106 
Interstitial keratitis, 84 
Intestinal troubles, 83 
Intramine, 90, 103 
Iodine, colloidal, 13, 18, 56, 65, 

76, 77, 87, 96, 99-101 

in alcohol, 18 

in animal organisms, 78 

oil, colloidal, 99-101 

stainless, 77 

tinctures, 77 

" lodism," 99, 101 

lonisation of drugs, 76, 79 

Ionised state, 79 

Ions, 79 

Iridium, colloidal, 73 

Iron as protein compound, 88 

carbonate, objections to use 
of, 89 

colloidal, 12, 77, 88, 89, 106 

compounds, 89 

hydroxide, colloidal, 1 2 



Iron in animal organisms, 78 

in human organism, 88 

solutions as remedies, 77 
Isinglass, 64 

Itch, Dhobie's, 101 

Jones, B. Seymour, 86 

Kala-Azar, 90 
Keratitis, interstitial, 84 
King-Turner, A. C., 97, 106 
Kirk, E. W., 90 

Lact-albumen, in milk, 21, 22 
Lead, colloidal, 12, 73 
Lecithin, 13, 48 
Leishmonnoris, 89 
Lesions, 85, 93, 101 
Leucorrhoea, 86 
Levinson, W. E., 90 
Linder and Picton, 1 2 
Liniments, 46 
Lipoids, 87, 104 
Lister, 36 
Living organisms, 2 

and dead organisms, differ- 
ence in action, 1 6, 17 

Livingstone, Dr. McFarland, 93, 


Lottermoser, 15 
Lupus erythematosus, 100 
Luton, 97 
Lysalbic acid, 7 

McDonagh, J. E. R., 87, 91, 103 
MacLeod, C. E. A., 83 
MacMunn, J., 86 
Magdalene blue, colloidal, 1 2 
Magnesium, colloidal, 73 
Malaria, 88, 106 
Malignant disease, 102 
Manganese, colloidal, 90-95, 96, 

98, 106 

Mastic, colloidal, 1 3 
Mayen, 19 

Mayer, Schaffer and Terroine, 20 
Medical possibilities of colloids, 

50-52, 1 8 
Medicine, use of colloids in, 18, 

45, 52 
Membranes, permeability of, 2, 

3, ii, 17, 24, 43 
Meningitis, cerebro-spinal, 86, 


Merchal de Gers, 96 
Mercury chloride, 78 
colloidal, 73 

colloidal, 12, 70, 71, 73, 76, 
80, 86-88, 89 

compounds, 47, 77 

cyanide, colloidal, 73 

ointment, 84 
Metabolism, 96 

Metals, colloidal, activity of, 79 

catalytic action of, 79 

effect of, on blood, 79 

germicidal power of, 69 

use of, 77 

Methylene violet, colloidal, 12 
Micrococcus catarrhalis, 88 
Micro-organisms and disease, 


Migration of particles to elec- 
trodes, n, 15 
Milk, asses', 22 

coagulation of, 47 

cows', 21, 22 

human, 21, 22 

lime water in, 22 

protective colloids in, 21, 22 
Miller, 25 

Molybdene blue, colloidal, 12 
Moore, no 

and Roaf, 2 

Morris, Sir Malcolm, 85, 91, 93, 


Mud, precipitation of, 33 
Mustard gas, 91 

Nanes, 25 

Nasal catarrh, 83, 86, 100 

Nausea, 99 

Necrosis, 82 

Nervous diseases, phosphorus in, 


Netter, 104 
Neuritis, 102 
Nickel, colloidal, 99 
Nucleinic acid, 28 
Nutrient broth, 70, 72 

gelatin, 73 

Obesity, 97 

(Edema of the face, 91 

QEdematus bulbar conjunctiva. 


Oil emulsions, 1 3 
Ophthalmia, gonorrhceal, 83, 93 

purulent, 84 


Organisms, animal, 13 

living and dead, 43 

structure of, 2 

vegetable, 1 3 
Ostwald, Wolfgang, 6, 20, 26 
Otitis media, 83 

Oxides, colloidal, 105 
Oxygen in blood, 26 
Ozone, 31 

Paal, 95 

Palladium, colloidal, 73, 76, 96, 

97-99, 1 06 

Parasitic affections, 101 
Paratyphoid fever, 97 
Parchment as a membrane, 3, 16 
Pellicle, 26 
Pepsin, 47 
Peptisation, 54 
Peptones, 7, 16 
Perineal eczema, 85 
Permeability, selective, 2, 3, n, 


Perrin, 25 

Petroleum, emulsions of, 46 

Phenol, 67, 68 

Phlyctenular conjunctivitis, 83 

Phosphorus in the animal or- 
ganism, 78 
nervous diseases, 48 

Phthisis, 1 02 

Picton, 12 

Piles. See Haemorrhoids 

Platinum black, 79 

colloidal, 12, 73, 79, 97 
Pleuritis, 97 
Pneumococcus, 88 
Pneumonia, 104 
Podophyllin, tincture of, 45 
Poison and reactions of metallic 

sols, 42 

Poisoning, 42, 78 
Preparation of colloidal sols, 53- 


Prostatic gleet, gonorrhoeal, 86 
Protalbic acid, 7 
Protalbumoses, 43 
Protected colloids, 1 5 
Proteins, 60, 87, 102, 104, 105 

colloidal, 107 
Protoplasm, 2, 23, 24, 25 
Pruritis ani, 85 
Prussic acid, 78 
Psoriasis, 103 
Puerperal septicaemia, 85 

Pupendi, granulama, 90 
Purgatives, 47 
Purulent ophthalmia, 84 
Pus, 94 

cells, 71 
Pustular, eczema, 83 
Pyaemia, 99 

Pyorrhoea alveolaris ,86 
Pyrexia, 97 
Pyrogenic cocci, 88 

Quincke and Helmholtz, 10 
Quinine, colloidal, 76, 105, 106 

disulphate, 62 

hydrochloride, 80 
Quinsies, 86 

Rachlmann, 25 

Radiations, action of, on sols, 19 
Rahe, 25 
Rayleigh, 19 
Rennet, 22, 47 
Resenschack, 20 
Resin, colloidal, 13 
Rheumatism, 78, 100, 102 
Rhinitis, 86 
Rhodium, colloidal, 73 
Rigg's disease, 86 
Ringworm of the body, 83 
Roaf, 2 

Roe, A. Legge, 83 
Rosaniline hydrochloride, col- 
loidal, 12 

Saline matter in the organism, 
107, 109 

solutions, use of, 107, 109 
Salt, action on colloids, 43 

decomposition of, 9 

water, electrolytes in, 3 3 
Salvarsan, 104, 105 

S chaffer, 20 

Schlcesing, 33 

Scirrhus, 95 

Scopolamine, 84 

Seborrhoeic eczema, 90 

Selective permeability, 2, 3, u, 

17, 24, 43 

Selenium, colloidal, 13, 73 
Semi-colloids, 7 
Septicaemia, 83, 85, 86 
Septic tonsilitis, 83 
Serum, 43, 51, 54, 107 

action on colloids, 65, 66 

immune, 39 



Serum, syphilitic, 60 
Settling, time of, 65 
Sewage, 29-32 

bacterial treatment of, 32 

nature of, 30 

precipitation of colloids in, 3 1 

purification of, 30 

sludge, coagulation of, 32 

nature of, 32 

Shellac, colloidal, 13 
Sherrer, T., 81 

Shingles, 86 

Shock, 107 

Silicic acid, colloidal, 12, 13, 64, 


Silk, electrification of, 7 
Silver bromide, colloidal, 12 

chloride, colloidal, 12 

colloidal, 9, 12, 56, 70, 71, 72, 
73. 75, 76, 77, 81-86, 103 

iodide, colloidal, 1 2 

metal, germicidal power of, 


nitrate, 84 

stainless, 77 
Simpson, W. J., 71 

Sizes of colloidal particles, 5 

Skey, 33 

Skin disease, coccogenic, 89, 90 

permeability of, 1 9 
Soap, 5, 7, 29, 33-35 

action of, 34 

hydrolysis of, 3 5 

nature of, 35 
" Soil," 38 

Sol, defined, 4, 16 

Solids with liquid properties, 6 

Soluble prussian blue, colloidal, 


Sores, soft, 83 
Spencer Herbert, 38 
Spirochaeta pallida, 104, 105 
Spring catarrh, 83 
Sprue, 83 

Stability of colloids, 50, 51, 66 
" Stability number " of colloids, 

64, 65 

Stannic acid, colloidal, 8 1 
oxide, colloidal, 104 
Staphylococcus pyogenes, 71, 91 
Starch, colloidal, 13, 64 
Stebbing, 20 
Streak cultures, 70, 71 
Streptococci, 71, 96 
Sulphur baths, 102, 103 

Sulphur colloidal, 13, 54, 55, 
73, 76, 101-103 

in the animal organism, 78 

ointment, 101 
Suppuration, chronic, 83 
Suppurative appendicitis, 83 
Suspensions and colloids, differ- 
ence between, 16 

properties of, 1 5 
Suspensoid particles, 6 
Svedburg, 20 
Syphilis, 60, 87, 100, 103 

Tannin, 25 

Tantalum, colloidal, 73 
Teague, 40 
Terroine, 20 
Thompson, 19 
Thorium, colloidal, 73 

hydroxide, colloidal, 1 2 
Thyroid fluid, 78 

Tin, colloidal, 73 
Tinctures, 45 
Tinea versicolor, 83 
Tin oxide, colloidal, 12 
Titanic oxide, colloidal, 12 
Tobacco disease, 36 
Tolman and Vliet, 62 
Tonsilitis, 83, 86 
Toothache 95 
Toxaemia, 85 

Toxins, action of electric cur- 
rent on, 40 

decomposition, 39 

destruction of, 68, 107 

diphtheria, 40 

nature of, 15, 39, 40 
Trench feet, 100 
Trituration, 53 
Tuberculosis, 97 
Tulloch, W. J. ( 41 
Turbinates, enlargements of, 86 
Tyndall, John, 61 
Tyndallmeter, 62 

Tyndall phenomena, 61-63 

Ulcers, various, 83, 84 
Ulcus molle serpiginosum, 90 
Ultra-microscope, 57 
Unsanitary conditions, effect of, 


Urea, 28 

Urethritis, gonococcal, 90 
Uric acid, protection of, 2 
Urine, 27, 28 

120 INDEX 

Urticaria, 85 
Uterine fibroids, 97 

Vaccine injections, 91, 92 
Valsava's inflation, 86 
Valuation of colloids, 57 
Vanadic oxide, colloidal, 1 2 
Vegetable fluids, 21 
organisms, 1 3 
Vincent's angina, 83 

Water, purification of, 29, 32-33 
Weimarn, Von, 6 

Wells, T. H. Anderson, 85 
Whooping-cough, 86 
Witte, 104 

Yellow fever, 36 

Zinc, colloidal, 73 

Zirconium hydroxide, colloidal, 


Zsigmondy, 20, 55, 58, 64 
Zymotic diseases, 36, 38 


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Under Pat. "Ref. Index File"